There isn't a difference really. Either would get your point across. If you want to split hairs, the first one sounds more like you donated money to a kids program instead of actually volunteering to help. The second one sounds like you volunteered and did actual work. If you really want to distinguish the difference, you would come out and say "I volunteered to help the kids programs during the summer" or "I donated to help the kids program during the summer." As they are, they both sound just as helpful.