We are an all-inclusive adults-only resort, and our staff does check the reservations because no one under the age of 18 is allowed to check-in to the resort.
Sonesta Great Bay Beach Resort
We were staying at the Sonesta in March and they became AI in October 2013 but as they are part timeshare their owners and anyone who has already exchanged would be able to bring children and while we were there children were in evidence! Funnily enough as there were only a few children we hardly noticed them and never at the evening meals.
Be aware - they advertise "Adults Only", but the staff do not check reservations - during the week I was there, there were at least 4 families with multiple children staying at the resort.
Also on the "All Inclusive" part - yes, it is, but they do NOT stock any "premium" brand beers & liquors as advertised (e.g. no Corona...since when is Corona a "premium" beer?)
Get an answer from Sonesta Great Bay Beach Resort, Casino & Spa staff and past guests.