Ronny, I suggest you closely examine how often you would need to fly your entire family in a six place aircraft, I bet it's not that often. The cost to buy and operate a six place over a four or two place plane will be huge for the few times that you would actually need all those seats. You'll find you'd be better off with the four or two place, and rent big for the few times you need it. Trust me, if you choose to take a weather or mechanical delay at some remote place, you'll be VERY happy that the whole family is not with you! And then there's the one kid who forgot to go before takeoff....
I have a wife and four kids, and have only ever flown a maximum of five of us at once (in a borrowed 182RG) a couple of times. Honestly, though in 39 years of flying I have never had an accident, I still don't want all of my family in a plane with me - just my choice, having seen too many cases where it did not work out at all well.
Give a lot of thought to your mission profile, you might find that "the big trip" can be equally well accomplished with some EasyJet tickets in addition to your plane, and for a lot less money....