My kids would not be on such a team. Period.

William, you know that I have strong issues with Islam.

OK, that's your choice. But just to play devil's advocate - let's say my daughter winds up playing soccer. She's on a team where many of the other girls and even the coach were Islamic. If they did a voluntary prayer before every game and praised Allah, my daughter (unless for some bizarre reason she turns to Islam, which I rather doubt) would quite likely just stand to the side and wait, and then "play ball". If that's all there was to it, I don't think I'd have any objection. (If it went beyond that, if it led to degradation/manipulation, then I think we're all against it).

Since we are talking about sports, I think it all boils down to whether these situations promote (or discourage) the good things about sports: fair play, sportsmanship, competition, building character. I've known coaches who brought out the best in these (with and without prayer), and others who brought out the worst in them.

My wife (who is Jewish) quit playing active sports in her teens because she was told by the mother of a volleyball teammate that she would burn in hell. So Christians can be nasty as well.