I've just spent two days with four kids at an indoor water park. Here's what I've learned: 

1. You're gonna get wet. Deal.
2. A bit of planning beforehand will save lots of time and money later. 
3. No matter how much planning you do beforehand, be prepared to change the plan when you get there.
4. Pack a lunch. (Thanks babe!) 
5. It's all fun! Enjoy it. 

Feels like all of the above applies to basically everything I've ever been a part of.