You have some good ideas already. I did this with my daughter and we went to the Dollar Store and bought ribbons that we handed out for things like lowest score, highest score, funniest approach, coolest shoes, brightest ball, etc. We let the kids vote on the winners but made sure each child received a ribbon. Another idea could be to serve cupcakes instead of cake and let each child decorate their own with sprinkles or any sugar cookie decorations you use at Christmas. Finally, if you need something to keep them busy at the bowling alley you could give them questions like I Spy and have them find things in the bowling alley during the game otherwise you could do a scavenger hunt for them. My opinion is that you don't have to give the children attending the party anything if you don't want to, as long as you keep them entertained and safe that is what they will remember.