The app for Quickbooks is very limited and a monthly subscription is required.  I wouldn't recommend it. 

A better solution would be to either go with Quickbooks online and use the iPad to access it or you could use Splashtop on the iPad to access Quickbooks on your home computer.  With either of these options you will have full functionality of Quickbooks.  You can use Splashtop for free on your iPhone but you will have a nominal annual fee to use it on the iPad when you are away from the same network.  You can try it at home over wifi for free to see how it works.  I think you will be surprised how well it does work.