If you paid any out of pocket medical expenses/doctor/pharmacy (not including dental) for the children or your wife, minus insurance premiums, you can submit those bills for reimbursement. Call the ChampVA folks, they have always been friendly and helpful, at least that is my experience.
Effectively, your benefits for ChampVA began the date of your 100% service connection. It can be worth the extra effort; I was able to recapture five years worth of out of pocket dollars.
The opportunity to return to school is exhilarating! I'm just about done with my AA and moving on to my Bachelor's program in a few months. Not only will your family benefit from the tuition waiver, the VA will also pay a stipend to your wife each month and when the children are old enough, they too will receive the benefit.
We are very happy for you!
Congratulations and welcome to the new normal.