OP here. Thanks for all the responses!!
A few answers to some of the questions raised. Putting pockets in the sundress is a great idea! I'm going to take the dress to the tailor tomorrow and see what he can do.
I am not a practical cargo shorts kind of girl! LOL! In fact, I don't like short at all. We go to WDW a lot and I have an arsenal of comfortable, easy to pack sundresses and flip flops that I bring (yes I can walk in them all day). I love that I can throw them on and my outfit is done. I typically carry a le sportsac cross body that is roomy enough for all of our ponchos, water bottles etc.
I'm wearing a vintage 1970's Star Wars sundress for SWW. I found a few iPhone cases online that have a small pocket for bills and slots for 2 CC's, plus a wrist strap attached. That's all I need. I'm going to get one of those and have DH put it in his pocket. If we still have to go through bag check, that's fine, but I'll give it a shot.