When a family signs up for camp, you send a confirmation packet, right? Maybe your packet includes a Parent Handbook, instructions for what to wear and bring to camp (packing list), a payment receipt and all that. But does your confirmation packet serve as a word-of-mouth referral generator too?
Here's how it can. When a family gets their confirmation packet, give them all the usual stuff I just mentioned. But also include a Customer VIP or Referral Card which entitles their friends to a 10% discount off camp tuition.
(Actually you can include anything else you want in your confirmation packets, but your guiding thought should be "what could I give just-enrolled families something they'd share with their friends?").
If your customers can say to their friends, "Hey, I just signed up for this great camp, and I can get you a discount so your kid can go there too," bingo! You just hooked another enrollment, and you didn't have to do a thing to get it. (Don't worry about giving 10% off, because you're probably spending a lot more than that to get a new customer anyway. So this strategy ends up being a bargain for you.)
I hope you give this a try. It's a VERY easy way to get generate viral word-of-mouth right in the middle of camp enrollment season. You really can't beat this as a core part of your referral marketing plan.