I always give students the option of choosing an alternative reward. I also, what to assure you that I have made accommodations for any food restrictions. I try to change up the s'more parties too. Sometimes it is a s'more (half sized not a whole graham cracker), trail mix, etc. One time last year we read "If You Give A Pig A Pancake" and I made s'more pancakes in the class that week :). I want them to be excited about each "party" so they stay motivated. They all really like it so far. As they year goes on our goal will continue to grow. I tell the students we can only add on to our goal we never subtract.