It’s going to be very difficult until you /your older child have a green card. Once that happens, your child is eligible for federal funding, work-study etc. until then, it may be hard to find funding -you might have to do some kind of personal bank loan. If you have a mortgage, consider a heloc (not ideal of course). Also note that visa holders - even those that are resident somewhere and can qualify for instate tuition (this varies state by state for H4 visas so you need to check local rules ) - are considered international students and disadvantaged in admissions. Do you have any idea how long it is expected until you can get your green cards?