I doubt there'll be much concern on that front. Star Trek has always been on the family-friendly end of the spectrum, and I don't think had even a PG-13 rating on a movie until First Contact (and that mainly for adventure-movie violence.)
I know what you mean by Trek being approachable to the entire family, but I think TMP was initially given a "G" rating when it came out, and that's a killer at the box office for a sci-fi action movie, too.* The TMP DVD's carry a PG rating, now.
This movie could probably be made PG and be great. Abrams certainly knows what lines to cross or not cross to manipulate the movie's rating. But a PG-13 is probably thought to help at the box office, so that's what they shoot for. Notice that most action-adventure movies of the XI genre these days carry a PG-13 rating. It's like a seal of approval.