"Will we all fit?" is a safety limit, not a preference

Publish the maximum per room type, as a number

Not "family rooms available" but the maximum occupancy of each room type, counting adults and children separately where the hotel does. A number lets a family decide in ten seconds; a phrase makes them write an e-mail. The figure exists already because it is tied to fire regulations, so publishing it costs nothing and prevents the worst arrival a hotel can have.

Say what an extra bed actually is

A rollaway, a sofa bed, a cot or a mattress on the floor are four different things and a guest who expected one and received another is justifiably annoyed. State which it is, the age range a cot suits, and whether the room still has floor space once it is in. The last of those is the detail hotels know and guests cannot imagine.

Children's ages are the whole policy

Under two, under six, under twelve: nearly every occupancy and pricing rule turns on an age threshold, and the guest cannot guess where it sits. Publish the thresholds and what each one means for sharing, for breakfast and for price. A family comparing two hotels will choose the one whose rules they can understand without asking.

Never promise an interconnecting room

Interconnecting and adjacent rooms depend on what is free on the day, so a request can be noted and never guaranteed. This is the promise most often made casually and most often broken, and a family split across two floors remembers who told them it would be fine. Say it is a request, say when it is confirmed, and never say yes in advance.