People were suggesting that he change his business to "update" it for the teens. He is indeed trying to update his business, for the crowd that actually spends money. I know several people who would love it if he were able to get the license and hold tournaments and league there. I hope that answers your first question.
If the skating rink is more for the younger kids, rather than the teenagers, then wouldn't they be picked up or dropped off? If so, then why are people worried? It's not like the two crowds are going to mix and "hang out" together. Not sure how a fence would work, aren't they across the street from each other and again, I don't see the need for it. I have no idea what the community center offers, I don't have any kids, so I don't have any reason to find out.
I understand you don't like alcohol and respect that, but I still think that you are combining images of plastered, ignorant jerks with pool players wanting a few. I doubt there would be a need for security. Honestly, these people aren't going to be there looking for fights or causing trouble. They are going to be there to play pool and have a good time. I think the owner already talked of putting a grill there if he can get the alcohol and things pick up.
If there are teenagers who really will miss the pool hall, why not find out if you can get one in the community center? If they don't have the money, have the kids do a fundraiser. If they raise the money, it can be an open table too.