It can be difficult to find a party favor for a boy's birthday party, keep it simple and give them all personalized tumblers. Personalized tumblers are a fun and useful favor that every party guest will love. Pick a design to go with your party theme or just pick a neutral pattern, either way, you can find just the right personalized tumbler to commemorate the day.
Hosting a party for your child is already a big deal, you shouldn't have to deal with clean up too. Keep it simple and give each guest a personalized tumbler. That way, they can just fill it with a drink of their choice and keep refilling it for the whole day. They can be responsible for keeping track of it and you won't be throwing away paper cups all day.