Another alternative if you want a quality boat, that will fit more of your 'family requirements' is a Shakespeare 650 (21 footer) (this is a hardboat though!)
Martin Curry on this site had one for sale a while ago, don't know if he still has it.
They're beatifuly made, beatifully styled, good hull design, great performance, sunbathing area for the missus, and if you choose to stay over on the island, or anywhere, it has a wee cuddy cabin to bed down for the night, camper hood etc, a real weekender. It's a stern drive though, so a little thirsty, but I think Martins one only has the 4.3l V6 motor, which was the smallest option for that boat.
They really are a lovely little boat, built by a decent manufacturer who cares about his product (Shakespeare/Francis Whitley), will be perfectly safe, contrary to what some idiots on here might want you to believe (their minds are damaged) and would serve far more family purposes than an open work boat (rib) or stupid bowrider.
Here is the advert from Martin, as I say, don't know if he still has it. He's a nice honest guy, so I'm sure it's a genuine boat.
Oh, and by the way, it's 3.5k under your budget.