Mattsmom, don't beat yourself up for feeling jealous. It's hard to see your dreams put aside over and over again at the expense of others, even if they're your loved ones. It's only natural that you'd feel resentful, passed over, etc. Your feelings are perfectly justified.
Now, that said, you do have a bit of a dilemma on your hands. I agree that it's never too late, but here are a few thoughts...
1) You and difficult child both start university at the same time, and both of you go part time and work part time. You'd both be able to help finance the school tuition, difficult child would graduate with valuable work experience and life skills.'
2) If it's not feasible for difficult child to hold down a job while going through university, apply the same suggestion to easy child's university.
3) Look into grants for mature students. Not necessarily through the university. There are TONS of scholarships available through private organizations, foundations, etc. Some have bizarre qualifications, but it's worth doing the research to find out if you can have your tuition even partially funded.
4) If you get a job at a university in my neck of the woods, then you and your children are entitled to free tuition. Whether you're a professor, librarian, janitor or what-have-you, the same rule applies. Maybe you can look into jobs at a university either near where you're living now or where you will be posted during S/O's 2 years. Even if you only get free tuition for 2 years, then that means you and at least one of your children don't have to pay, and you can apply the money to the remaining years.
Just tossing some ideas out there. You can find a way to do this.
Trinity