Advice for distance events at the end of meets?

Hey everyone! I'm coaching at a fairly large age-group (mostly 8 yr-17yr) meet this weekend, but I also got talked into swimming an Open 400 Free race at the very end of the meet on Sunday. I haven't raced in a while, and I'm really just going for a time (sub-6 would be nice), but it'll probably be a good 3 hours or so from the time I get to warm up until my race. There's also no warm-up/warm-down pool, and the whole time in between I'll be coaching on deck... Any suggestions on how to stay relaxed or ready for my race without being able to get in the water? Also, any suggestions for what to eat (breakfast, snacks) to keep energy throughout the day? I'll probably eat breakfast around 6:30 am, warm-up around 11 am, and then swim my race around 2 pm or so. Thanks for reading :)