We always have peanut butter Ritz crackers dipped in white chocolate with sprinkles on top. It's a lot like Catherines pretzels but using peanut butter crackers instead.
Lainey loves to help make these and now that the boys are older, they will be helping too. I always let the kids spread the peanut butter with plastic knives from to-go orders and then they sprinkle to their hearts content. HUGE mess but the kids love it.
There is also a ton of things you can do with Rice Krispie treats during Christmas. Dye the melted marshmellows green and use a Christmas tree/bell/wreath cookie cutters to make shapes and then decorate, decorate plain treat squares with green and red icing, M&M's or sprinkles, etc.
Beth