i have checked in a few marriott properties that had handouts (and postings) for do and donts when kids were a major component of the population - doesnt bother me.
the hotel isnt crazy - they know where the hotel is and who stays there (teams) - but they also dont want it to get out of control - which is pretty easy. just because they advertise their proximity doesnt mean that is why they built the hotel there or that it is ok to be a clubhouse. The other 9 months out of the year it is business people i would imagine
i have also been with AAU BBall teams (my daughter played) and I know what goes on in hotels with tons of kids - slamming doors, running around. the breakfast buffet disappearing in 5 minutes- sometimes a little, sometimes alot
all that being said, the manager should address your concerns in person. was there a specific incident that prompted your (their attitude) finding the GM? did you have a copy of the rez confirming the rate?