Moodies, like Bristol and probably other brands, went up-market in their later years to find buyers so there is a difference between the older and newer. I have a friend with a Moody 345 and it is a very nice boat, although would seem a bit tight with two growing kids for me. Also the three cabins in a boat like this are the fore, aft and main, so the parents end up sleeping in the main cabin which means that the dinette table needs to be folded down every night - or you sleep on opposite settees. A big advantage of the charter boats is that there are many with three sleeping cabins.
If you were to buy an old charter boat it would be a good idea to be somewhere with good access to boat bits. There are very good marine stores in St Thomas, St Maarten. and Grenada. You could go out there ahead of the family to do the work needed - and there would be work needed.
In South Africa doing lots of boat stuff. Departure north from Cape Town around December 15th. Arrival in the Caribbean around the beginning of February, after 5300 miles or so.