Our kids went deeper than 40' but since a lot of the dives are wall dives, it is easy to stay at 40' even if most of the group is below you.
That's how I do it. Staying above is indeed staying with the group.
The closer to the surface, the more life there is. It's really up to the dive buddies to set their profiles and depths. If you hire a personal DM, they will do your bidding.
40 foot is no magic safety limit. I would advise that you go beyond the quantitative measurement of depth and consider what you are really most concerned with. If someone gets in trouble at 40 feet or 5 feet, they're still going to be in trouble. If I am commercially assigned to chaperone a juvenile at
any depth, he
will surface and see the sunset. It's a matter of attentiveness and supervision until they can manage their own safety. I dive with specific adults on assignment that I must watch like a hawk- they have
zero dive sense but they have the desire and wherewithall to "make it happen".
I have seen motivated and aware young ones have a ball when they are given access to a local DM and a magnifying glass. It might cost you $20 per dive (in a multi-dive package if you shop in Roatan), but well worth the expense.
You don't have to go deep to have a good time, but there is
nothing present to prevent any diver from exceding their limits. A DM can only do so much on a group dive, a
private hire DM is a whole different deal. Might be well advised for at least the first three days... then turn the puppy loose under
your close supervision. Then let the kid be
your guide!