So if you watch for Mathis Brothers, they do a renewal drive every year and it's at a discount. And you usually get some little stuffed animal or something for the kiddos too. You do have to go to the store to do it though.

I'd encourage anyone doing one, to look at the Science Museum as well. Only 1 or 2 trips, just like the zoo, and it's paid for it. And with the family options, you can let Grandma take them on your membership too. There are some rules around that, but it's great. And the SMO pass is good for discounts or free entry at a LOT of other children's museums around the country (zoo pass for zoos too) if the place you are going is a member of those groups. And even if they aren't, sometimes if you ask, they'll discount you anyway.