This is the PERFECT answer to this summer’s “I’m Bored” complaint. They’ll be off hunting for a good long time, and the young ones will be reinforcing their alphabet skills in the process. Older kids will just enjoy the hunt. I particularly like this for outdoors- it’s harder.
Do be sure to set some rules– i.e. no picking the neighbors flowers, no crossing the street, etc.
Having a birthday party in the park or some other outside venue? This would be a good party activity PROVIDED you set limits on where they can go. Send them off in teams to keep them together. Give them a time limit, tell them they WON’T be able to get every letter but the team that gets the most will be the winner.