I checked out the Walmart gift cards. They don't expire, and can hold $10 - $2500.

Sounds like a plan.
We'll probably start this early ourselves - be prepared. We hope that when that day comes we won't have to use formula, but you never know. All kinds of things happen to change the best laid plans.

It's better than a savings account at this point in time (with taxes, sorry interest rates, fees, hassle...).