There are many non American
DVC owners, the largest single blocks are from Canada and the UK.
At the moment Disney itself is only selling Saratoga Springs, and this has a "shelf life" of 50 years. All other resorts ( OKW, BWV,BCV, VWL, Vero and Hilton Head) are available through various resale agents. These resorts only have 38 years left to expiration, so the price should reflect this fact. I don't think buying from abroad for a resale should be an issue, I know of many Brits that have bought resales without any problems. I am sure the agents are used to dealing with those situations.
The number of points you'd need is VERY dependant on the size unit you would like. A studio ( basic hotel room size) is about half the cost of the much larger one bedroom unit (seperate master bedroom with en suite, fully equipedkitchen,living/dining area). Studios cost between 8 and 15 points a night on weekdays and 20-35 points on Fridays and Saturdays. One Bedrooms roughly 20-30 points a night weekdays and 35-50 points Fridays and Saturdays (check the DVC points calculator on
http://www.wdwinfo.com/resort/dvcpoint.cfm for a more exact point cost for your individual style) . A 2 bedroom unit goes from about 25-40 points a night on weekdays to 50-60 points at weekends.
Coming from Denmark I would think it likely you'd be coming for a reasonably long stay, and would do many "non Disney" things. It is therefore worth taking into account the points savings to be made by not using DVC on weekends whenever possible. this may mean you'd decide (depending on flights) to check into say Universal's hotels for a couple of nights at the start/end of the holiday avoiding the high weekend points costs. I tend to use DVC as a highlight to a trip, stay at other places (I-Drive, Universal, the beach or at a holida villa/home) for some/all of a longer trip (three weeks or more) and spending 5 days on WDW in a DVC home and maybe a few days staying at the DVC Vero beach resort. Some people don't like moving location, so I understand that may not be an attractive plan for everyone.
In Feb/ March . A ten night stay ( only 2 high point cost nights) in a one bedroom @OKW would cost you 284 points. A 5 ( low cost) night stay would cost you 110 points. A 2 bedroom ( same days, same resort) would cost 384 for one 10 night stay, or just 150 points for a 5(low cost) nights stay. With banking/borrowing, using cash nights here and there and mixing up the room sizes at times I think you should be OK with 150-200 points if you think a one bedroom is enough and maybe 230-280 points if you'd like a 2 bedroom unit.
Again it's worth remembering your boys are already in their teens are it won't be very long until you may well just be needing rooms for just two of you, although the counter to that is that it may not be that long until they have families of their own and you might like to take them and their children away. I would always suggest that people go on the lower end of their estimate for points needs as you can always add on some points reasonably easily if you decide you need more, it's a little harder/more expensive to get rid of points you decide are surplus to your needs.
Use year I would suggest August/Sept/Oct would all be workable for you. That way should you're normal times get cancelled for any reason you would still be able to organise a trip in the summer holidays to use your points up.
