Lose weight quickly without much exercise?

I have been eating very healthy & going to spin classes 3 times a week, along with walking a lot. I've done this for about two months and lost about 15 lbs. My goal is to lose 15-20 lbs before school starts up again. The issue is I'm going off to a performing arts camp for a month and won't have any time for exercise. However, I will be walking a lot, and maybe doing some recreation activities. I really need to lose this weight, and after I get back, I'll only have a few weeks before school starts again. Any advice on what to do?