After 14 views, I thought someone might let me know if I am close to being right. So I'll try to answer my own question.

After the #1 child receives her funds (about 7200.00) I will give the other two an imaginary $7200.00 and keep a yearly record of past years interest rate and add it and the differance between that the inflation rate if any to the principal. So in summary:

$7200.00 + estimated 3.75% yearly interest rate (compounded monthly) + any differance between interest rate and inflation to be added to the new principal. This is about as close as I can figure it.

So to make this work, I will also have to adjust the monthly deposit to reflect this new principal.