Vehicle choice in my opinion is something that takes a lot of thought but, most importantly lots of very honest discussions between you and your wife.

Things that need to be considered:

Route and terrain.
If you're going to be on tar/good gravel roads the whole time I would consider a RWD Sprinter self build. These days you can literally buy everything you need to fit it out straight off the shelf in Europe unless you wanted to go down the custom route but it easy and so much so that someone with basic mechanical knowledge and a bit of common sense can do. These are also going to be far more comfortable for four of you and much more fuel efficient therefor you will be able to spend more of the budget on traveling for longer or doing more activities which will make the trip more enjoyable for everyone.

The next level up is a 4x4 sprinter again it has all of the positive features discussed above just slightly worse fuel economy and tyre wear but better access to more remote places.

The next step is in my opinion then a truck. Something like a Mercedes Benz 1017 with either an extended cab self done depending on your skill set and confidence levels but, it doesn't need to be massive like a fire truck cab. Just big enough to fit a second row of seats and maybe some kit storage.

Personally if you have the skill set there is nothing more satisfying then building your own vehicle but it needs to be remembered that it comes at a cost, whether that be financially or time away from your young family and if your planning a trip like this it's most likely that you are a loving family man an want to spend time with them. that's just my assumption.

The level of comfort you want and need.
A family that is happy when travelling will travel more. By adding some little creature comforts it will make the whole experience more enjoyable for all involved. This means things like possibly fitting a heated outside shower so when you all come back muddy you can wash off and someone doesn't get upset because they've just cleaned the vehicle and now it's all full of mud again. Kids also need need more water and therefore this will need to be considered. there is loads more but I just wanted to give you a feel of how you should be thinks at this stage.

Budget
Budget will play a massive part in you're decision making process. Trucks are alot more expense but if you have the money great if you don't you will need to do more or want for less, but it's not all as scary as it looks. Again depending on you skill set and level competency.


Maintenance and your own ability to maintain repair it things. You can go on corses to learn to do basic maintenance and spanner work. Failing that you can learn how most people do these day. Youtube and making a few mistakes.

I hope this helps. Just don't rush it and know that not all your decisions are going to be the right ones and as long as nobody dies it's all part of the adventure.

Alwyn