Please, DON'T TOUCH

I would ask the parents ahead of time to ask the child not to touch, but instead to ask if he/she would like to listen to some music.

If they are interested and end up touching your stuff the best approach is just to remind them to please come get you if they want to listen to music.

If you feel that the child in question is unlikely to obey (and I'm not judging the child here .. some kids are more inquisitive, and push the boundaries more than others) then I'm afraid the only answer is to move your gear temporarily into a room that is designated as off limits.

Watch out for small toys going in bass reflex ports as well. A friend of mine had to have his Kef reference speakers dismantled at the Kef factory to remove toy soldiers.

Me??---I would disassemble the system,place it in a closet,speaker drivers facing a wall---this way you don't have to repeat the "don't touch".

I had a babysitter snap the cantilever off of my cartridge while playing LPs for the kids. It's a difficult situation. Our home was more or less 'child-proof' where the knobs, and TT were well off the floor.

Would it work to just unplug some of the gear, say the amp/pre-amp. If you have a TT that is within reach of little fingers, you would be better off to put it away. No parent is going to let their child ruin something, but why take a chance with a whoops? Make sure speakers have grill cloth on, and are solidly placed. It hard with stand mounted speakers. Kids could knock them off the stand.

Use whatever precaution is available, just asking might not be enough, and there is no sense loosing a friendship over a week without the system. Good luck.

Its simple tell the kids parents that the stereo is off limits

The key is to avoid to tell them DON'T TOUCH. No matter what way you mention it they would feel uneasy to stay at your place.
Disassemble the whole system and put them in the corner with drap cover it.