The DTV would tick every box and your family would get visas as your dependents. Educational visa is an option if you don’t have the funds in situ to show for a DTV but it’s more faff and an agent can do a work around for that for you anyway to still get the DTV.
go to BKK instead and then get a cheap internal flight to Phuket, you will probably find it works out a lot cheaper. Have a night or two in Bangkok even, make something of it.
Some airlines, if you book direct with them, like Qatar, give you a free hotel for your layover. I go from London to BK via Doha with Qatar for about £700
