A cruise could work really well for your family - p and o and Tui marella have reasonable priced ones -
For your DS15, there will be new places almost every day to walk round, plenty of shade on the ship and always things to do indoors if he doesn't like the sun - always other teens on board if fancied making friends, playing games etc but equally as easy to do things on his own, like cinemas etc
For your DS12 there are pools, kids activities and loads of things to keep him amused - out last one had an arcade and escape room on board
For your husband, it is really east to manage dietary requirements on the ship, the chef speaks to you every night about the next days menu to check its suitable
For you, theres so many ways to relax on board, spas, quiet spots to read, nice bars and cafes, and the entertainment is so varied throughout the day
For varied families it can be ideal, and its so safe as the cant go anywhere so can have the freedom of the ship.