Annual week long family reunion...

Talk to the person in charge. Might be your aunt, maybe your mother, whoever runs the reunion. Tell them how its not fair that you have more chores, and how since you're the only ones with kids you should maybe have less then others. Try not to sound nagging, but stay strong and don't give in, at least until a reasonable compromise is approved. Don't back down, and stick to your opinions, even if it means hurting the ones you love. If they have had kids, remind them. Try to do it before-hand, so the option of a flat out "no" doesn't exist for the other side. Hopes this helps. (sorry if its a little rough, this is coming from the perspective of a 28 year old lawyer)