Have stayed at lots of hotels.
Have been in a lounge filled with kids. All sitting quietly at their tables eating breakfast - not a problem.
In fact, I find more people who think that the lounge is the perfect place to hold their dry run of their demo or do a conference call on their speaker phone much more annoying.

But anyway, if you see kids running amok in the lounge, talk to Marriott and ask them if they know who their parents are.

If it is just that it is crowded, then that is why you travel on business - so you can head down to the restaurant and pay for breakfast and eat in piece.