1) I don't know much about being on a sports team as an adult or parent, but the site feels snappy so I like it :)
2) It definitely sounds like you're solving a problem a bit more general than just sports teams, so you may be selling yourself short. It sounds like something that could be used for any kind of 'meetup' style organization (where there are some scheduling issues plus some financial issues). I remember needing something like this many times in college when everybody was a part of a million different student organizations. So... you could make the main pitch more general but than have a sports team as your primary case-study.
2) In my humble opinion, you aren't likely to do anything with photo sharing that hasn't been done before, and it doesn't look like you're very focused on it anyway. If it was me, I wouldn't bother with that aspect.