Re: Abacos or BVI
I've done both, Abacos and BVI. Chartering, Capt'ing, and deliveries. Hands down the VI's win, especially with the 5 year old. My daughter is 3 and we just got home after 8 days down there.
Don't discount the "land" scene. Most of the restaraunts/bars are VERY kid friendly and it gives the kids a great break from the boat, plus interaction with other kids. Ivans - White Bay, Beach Bar - St. John, Skinny Legs - Coral Bay STJ, Capt Mulligans - Nanny Cay Tortola, Pirates Bight -Norman Island, Leverick Bay Marina - Virgin Gorda are all perfect for kids and you'll see lots of them running around and playing. The VI's are way more kid friendly than the Abacos.
The Baths are another excellent shore excursion that the kids love.
Make sure you get a mask+snorkel for your little ones. Lot's of good shallow spots for them to play in the water and view the fish.