OK. The itinerary on Joy is much better, you are a single ship in Roatan and Belize. You are not going to be in Haven proper, but a short elevator ride will get you there. I believe a family villa will become available closer to the sailing date, and the price differential would be relatively small, so that you have a good chance to snag a really great suite for your family at a reasonable price.
There are often specials in the Haven restaurant (specials = new mains that are not on the menu) which could justify dining there over, say five evenings. At the same time, it is never as crowded as Luminae. For your daughter, there is a higher chance to make friends in the Haven than in the Retreat, if she wants to of course. Entertainment of Joy could also be much better than on Beyond, just look at their shows.
Bottom line, I would not hesitate to book Joy's Haven