Enjoy your meet! I'm sure you'll have a lot of fun.
As for stretching and mobility exercises, I do do some but probably not enough. I keep planning to sign up for use of the weight room at the pool but it would be hard to fit it in without taking time away from swimming. I own a set of light dumbbells which I occasionally wave about half-heartedly and sometimes I try a press-up on a chair or something. I used to be able to lots of press-ups when I was young, even the sort where you clap your hands as you fly off the floor, but I'd be hard put to do ten ordinary ones nowadays. Old age need not necessarily mean total decrepitude but it seems there has to be a certain amount of it. I don't believe I could do even one pull-up. I'd probably drop dead if I tried to run a hundred metres.
Thank heavens for swimming!