YeOldeTrout, if your DCs are US citizens they are eligible for institutional financial aid from individual universities (essentially a tuition and room and board waiver) as well as Stafford and the other govt guaranteed loan (can't remember the name) and the Pell Grant, plus possible work study (a campus job that you have to go out and get for yourself in competition with other applicants) plus individual outside scholarships that may be restricted to citizens.
Institutional financial aid varies according to institution and is means tested, but depending on income a student could get a completely free education. The upper income limit for most institutions is $150k afaik. The best universities offer need blind admission and promise to find a way for you to afford to attend if admitted. However, even at that, most parents and students end up taking out loans.
If any of your DCs is a young man, he will have to register for the draft before he will be eligible for govt aid.
To apply for all forms of aid you need to fill out a FAFSA in late December/ early January. Some private universities also require the CSA Profile to be filled out. Some universities both state and private require further income verification but this is usually after the FAFSA and CSA Profile have been processed.
If you are worried about loan sharks or dodgy loans, contact the Consumer Finance Protection Bureau. They may supply a list of reputable lenders for private loans. Many main street banks offer education loans.
The 'cost of attendance' is the figure to look at in US university prospectuses. This is the all inclusive figure -- tuition, room and board, estimated cost of books and materials, health insurance, and sundry other costs.
[Trinity College Dublin (and all other Irish universities) requires three years of residence in Ireland to qualify for Irish student fees. There are scholarships that can help out.]