enjoy your sex trip and I wish you happy bottoming! if you're not going to be doing too much physical labor during this time I recommend going full bottom mode: the week ahead of it start eating very lightly, initially a high fiber diet with added psyllium husk or metamucil. your body might be different but mine would say no dairy during this time. for the day before or even two, switch to a meatless and somewhat low fiber diet - ramen noodles is a classic, cookies, soup, other carbs. before you leave for the trip, clean out with an enema bulb (or store bought enemas if your ass is bougie or inexperienced). the combination of low fiber and low food throughput should keep you from having to poop and whatever poop is still in your tract will get largely removed by the enema.
while you're out at your fuck-tent, consume most of your calories from simple carbs as much as your body will handle so as to give your microbiome less to work with - applesauce is kinda nice, fruit snacks, white bread. eat like a twink!
remember to stay hydrated!! I know you're not trying to pee either but it's important to hydrate even if it means suffering whatever penalty your dom is giving you when you ask to be let out to pee