Dear Father Newlands - are you absolutely sure this is the best way to keep your family intact? Especially as they want to take a lot of luggage on their holidays....
How many hours do you have in your logbook driving a car? how many in your pilots logbook? would you trust a low time pilot with your family? be objective.
Teenagers get bored. There are no toilets on light aircraft. Passengers get airsick. Would your wife know how to land the plane if you were incapacitated?
I witnessed a family of six - Mom, Pop, 3 kids and Granny - try to fly 500 miles for a Thanksgiving Weekend. Weather intervened. Attempts to land at 3 different airports unsuccessful, the family returned safely, but nobody enjoyed it, not even the father; he was responsible for everyone's misery.
Suggest much shorter hops by yourself until you have lots of hours, then the odd naughty weekend with your lady love, say in Ireland where the natives are glad to see you and they speak English - or when you have a bit of mountain flying experience, Spain or Italy are not too far. Use the money you save by buying a Cessna to splash out on a really good hotel, or perhaps a few diamonds.....and without the kids she can take all the luggage she wants!