Did you know that volunteering to help homeless pets is actually a great summertime activity for kids? My person spent summers as a kid helping out at her local Humane Society--feeding dogs, cleaning cages, and taking them out for walks. Or you can do collections like Vincent. Shelters always need the help, dogs always need the love, and it teaches kids about the repsonsibilities of owning a pet!
Check with your local shelter to see if the smaller members of your family can help out. You can go to Petfinder.com and search by zip code to find all the shelters and rescues near you.