Good advice above, to which I will add:
Learning "Hava Naghila" would be a good idea, in the event they want to do the celebratory Hora.
Get parents and adult chaperones on your side from the word "go," enlist as many as you can for crowd control. No offense to anyone of the Jewish faith, this is just an objective observation based on experience, but the kids can get really wound up and out of control if there is not enough adult supervision and enforcement. I've seen the adults actually flee to the recesses and nether regions of the facility to have a cocktail and avoid the ensuing melee, leaving the poor entertainment to deal with all nature of bad behavior. At some mitzvahs, it's almost an expectation that the kids have a license to do crime and that the entertainment will tolerate and deal with it. As an owner/operator of a mobile DJ service for 8 years, I can't stress this enough. I put it in my contract that there will be ample adult supervision to avert inappropriate out-of-control youthful behavior and I make this abundantly clear to the client. If they don't like it, I decline the gig and they can find another clown to run their romper room insanity.
Charge what you're worth, every penny, because I can assure you, at the end of the gig, you'll have earned it.
