If you oldest is graduating THIS spring, you are already 3 to 6 months behind.   A lot of financial aid stuff needs to be completed by February, especially FAFSA and work study.   Plus many colleges and universities will give significant scholarships to kids with excellent high school GPA in hopes of enticing the student to enroll.

This late in the program, I don't have any advice, but hopefully others with kids still juniors or below will get some help.