My kids are now 12 and 5, but most of the experience is pre-pandemic and when my 2nd son was 3 or younger. Often in Asia and sometimes in Europe the room max occupancy will be 3 (hence the results you see on the website searching for 4). In those cases I email the hotel and check in advance. Every time except once the reply was it would be fine to book 2 adults 1 child as long as we can use the existing bedding (which we always could since we were traveling with a Shrunks Inflatable Toddler Bed). I think always better to confirm ahead of time.

I have also had some odd responses re: max 3 occupancy rooms. For example one hotel in Dublin said the room (kind bed + sofa bed) would be too small to add a crib or rollaway, but they would provide an air mattress if I wanted. And a couple times the response has actually exceeded my expectations - for example in Tokyo one property suggested we actually get a King room, they would provide a crib, and that the window had a very large bench seat that our older son could sleep on (and it did - the window area was as large as a single bed - worked great).

That said, we have reached the point where my wife wants her own bathroom vs. sharing with the kids, so Hilton's confirmed connecting rooms feature has definitely increased our # of Hilton stays vs. others the past 2 years (all domestic US travel). Often Accor properties will return a 50% off second connecting room rate if you search 1 room / 2 adults + 2 kids which can be useful in certain parts of the world (i.e. we have an upcoming Australia trip and it is almost all Accor properties).