As an atheist resident of Massachusetts and Connecticut for most of my life, and a transplant to South Carolina, let me just say that I know your pain. I have 3 sons, all of whom play sports. Most of the teams they've been on do a prayer before each game, even though I get annoyed by it. In a few years, I plan on starting a travel baseball team for my youngest (currently 4 years old) son, and you can bet cash money that we will never, ever pray before a game as a team. But if kids want to pray by themselves, I'd be fine with it.
What I tell my kids is to just go along with it. It's really not a big deal. If other people want to pray, let them pray. Your daughter can sit there and do nothing and it's all good. In fact, while I really like to see my oldest son hit doubles and triples, some of the proudest moments I've had as a parent are when their teams huddle to pray and I catch my son looking over at me and shaking his head just enough for me to see.
I keep my atheism to myself down here and I recommend you do the same for safety's sake. If you were single, independently wealthy, had no children, and not afraid of a backlash, then I would recommend the opposite. Only a select few people know that I'm atheist (really anti-theist at this point), and I keep it that way because I fear for my safety and for my job. I'm not joking about that. It's fucking serious. Make no mistake, you WILL encounter religious conversations. Prepare for it. Another thing to prepare yourself for... if you thought religion was simply false before and you had no emotional investment in the god question, living in the South as an atheist can and probably will slowly fill you with anger. Take it from me. I used to not care about religion. Now... Well... lets just say I care and leave it at that.