"don't look that great" is pretty subjective. What do users say? I'm too lazy to link to them, but you can easily find mountains of evidence that users hate downloading native apps. The cost of acquiring native mobile users is much, much higher than mobile web.

Creating a social network is really, really hard. Doing it on a mobile device is even harder, especially when there are already versions of this on social networks full of users (like Facebook). I use Facebook to organize pick-up sports games, and it works great.

You have huge obstacles here, and trying to get people to go to an app store and download an app doesn't have to be one of them.