Thanks for the replies everyone, I think the main thing will be to make sure they get some quality rest before, during and after a show! I usually feed kibble in the morning and raw at night so I might even feed them kibble the night before the show as well, or maybe add some pasta to their raw for the carbs.
I guess I could take some pasta with me too to feed them as treats during the day!
Supergirl, you said about the goats milk and water mix, is this meant for boosting energy or something else?
Stamina also must play a part, I'll have to start taking them out for longer to build them up to coping with whole days out! It's just awkward at the minute with Merfyn as he's not a year old yet so still on limited walks!