Well it's time now.

You're MIL (from your descriptions) is already well into Dementia. Granted there's other underlying medical issues, but here's what I'd do if it were me.

Get MIL in for a really good physical, see if meds will help.
     Aricept, heart, ulcer, etc.. have a Dr. evualate and determine the best course of action. Understand Aricept isn't a magic bullet I said above.  Alot depends on your FIL how healthy he is physically and mentally.

If you FIL is capable,, one option is having a caregiver(s) come in and help with the meals, cleaning around the house, dishes, etc...  so even if the FIL is physically/mentally capable,, he doesn't "HAVE" to. 24/7/365 will beat anyone down to a pulp, and be extremely depressing.  You,hubby, FIL, nor no one else should destroy your lives/health/happiness just to care for MIL.  (Your MIL would not want that, just as you would not want your kids sacificing their lives/health to care for you)

One thing that is VITAL is consistancy and Routine.  IF in home care is the decision, then set down think of everything that is done throughout the day/week.  Write it all down, and assign times to it. 

 Wake up 0600 Bath/shower

Breakfast 0700 Take meds,  after breakfast, do dishes, laundry, clean.etc,etc,,

Lunch  1200, do dishes, watch TV. (or whatever) 

Supper 1800  (military time)  clean table do dishes, watch T.V.  etc..

Bed time 2200

You want to make time for whatever hobbies/fun MIL wants/remembers/etc.. but main thing is to keep her as active as she is physically/mentally capable of every day, and with a very set routine.  As in cast in stone.   Your MIL will be able to be at home longer IF she has a very consistant routine.

As for the "ensure" and all those energy drinks,, they're ok,, but DO NOT let the energy drinks become a replacement for eating properly. Dr's are real quick to suggest "ensure" or the like,, but as with what alot of older people "hear" is.  " I'm prescribing ensure for you",, so the old folks will drink the damn ensure,,, be full,, and NOT eat properly !!! Simply because they're already full !!  Encourage good wholesome food first and proper eating !!  There will get to be a time when Ensure is going to be needed,,, but,, what happens is old people will drink ensure and their stomach's will shrink. (just like anyone at any age)  And,, prematurely,, constantly drinking ensure instead of wholesome meals just speeds up the process.

Again in the food department,, don't fall into the trap, "I only want tea and toast" (for example)  Meals need to be varied and not just their "favorite" foods or drinks. This is one area where you don't want to ingrain any "routine", different foods and vary them.  If a routine is developed in eating habits,, meals will become a battle to get them to eat.  

Eventually, FIL and caregiver's will not be able to fill the needs. Hard to hear, but this going to grind everyone down, and likely will be hardest on FIL.

As to giving up the checkbook....  legal stuff,, ugh..  ok.. Are your MIL and FIL's wills in place ?  How about the legal paperwork for "what if".  Both MIL and FIL are not spring chickens, so, "if it were me".. (again it's not)

Get a GOOD Attorney and have FIL set up as Guardian of your MIL. Also same time,, set up the paperwork so when FIL is unable to make rational decisions for himself, You and your Hubby will become Guardians of your FIL.  DO NOT let your Attorney talk you into "power of Attorney",, if he/she says POA is good enough. Say "thanks for your time", get up and leave !  Go find a good Attorney that will write up Guardianship papers.

The hard part of this is of course,, having your MIL and FIL agree. Your MIL may agree to having FIL as guardian,, maybe (hopefully) FIL will agree to you and Hubby being Guardians when he is unable to care for himself.

POA's is a POS, get the paperwork so guardianship's are set up. There is a plethora of reasons,, just a few,, goofy buying of KRAP,, they can't be held liable, You and Hubby would simply say, "nope,, we aren't paying $1000's bought off Homeshopping network". This one is a "biggie",, if MIL is in a dementia unit,, without Guardianship, she can simply say,, "I don't want'a be here, I'm leaving,, and no one can stop her".  If the Guardian say's thou,,,"MIL will stay here regardless of what she says or claims" and that is what will happen.

In simplest legal terms, whoever is the Guardian is legally the "parent" in every aspect of the 'ward's" life.  Say your MIL falls breaks a hip and refuses to go to a hospital,, your FIL has the legal authority to see she does go to the hospital even if she refuses.  The same will apply if your FIL has set up the paperwork so you and Hubby are Guardians.

This is a hard thing, how hard it is depends on both your MIL and FIL. and,, getting all the proper paperwork in order.

One thing I can say is, I guarentee ignoring or putting off the issue until it is too late is AWFUL !!  Much harder much worse trying to fix after the fact, instead of setting  literally everything up before it has to be done.

Red/Green has just touched "the tip of the iceberg" in his post.  I for one, know exactly how FUBAR  (if you aren't familiar ask hubby)  these situations can REALLY BE.

We all only get one life to live and everyone owes it to themselves to live it to the fullest extent. Which doesn't mean sacrificing lives for the parents. (physical-mental well being) Normally,,,,,,,, Parent's do not wish to destroy theire children's lives expecting the children to have to deal with all this type of krap after the fact. Parent's want what is best for their children and will do what is necessary so their children will have as good as or better life than they had.  Normally parent's do not want to be a burden on their children as the parent's are reaching the end of their lives, and will do what is necessary so their children do not needlessly suffer because of the parents. You don't want that for your children,, and likely your MIL-FIL does not want that for you or your hubby.

Hope this helps, Again,, sorry took so long to respond.

Edit: forgot to respond to the fever stuff, and exaserbating the dementia.  It may or may not, I've not read medial reports that say colds/fevers have any effect.  What I would do if the family isn't aware of your MIL's dementia is let them know what to expect. Especially so the grandchildren are helped to understand, it's really difficult and even harder for kids when "grandma doesn't seem like Grandma", or "what's wrong with Grandma??"  

Do try and make is as memorable as possible for your MIL and family. Her dementia will rob her of her quality of life way too soon as is, make the most of the time you all have now. 

Don't ruin your own health worrying about holidays, do the best you can, and enjoy as much as possible, you any your family.

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