NZ, you made a good decision re: your family, and having the plans set this far before the twins arrive will give you much peace of mind. I admire you for knowing your limits!
I was so concerned about my GD going into preschool at age 2 just so her momma could keep working. But her school has been great and she has really thrived. You are right about how wonderful those classrooms are, with all the bright color and activities. And good teachers are worth their weight in gold! So your girls will have something fun and new to look forward to. Hooray!