Well with the ages of your children it will be ages before they run out of legroom anywhere !
I'd say the XC90 has a measure of street cred but isn't anywhere near so stylish and sporty as the new X5 I drove last week . For me, if I have to drive something big I want a bit of fun too. Shallow but true.
I'd say they are of similar dimensions overall and while big enough for a family of 6 + nanny, wouldn't be as cavernous as eg a Praevia. But MUCH more fun to drive...
My XC90 has a good residual value - but diesel v petrol would have been better...
The BMW dealer told me the diesels will hold their value well; we are very tempted to get one. BMW build quality is superb.
In the Volvo I plan on putting the 12 and 13 y olds in the middle row soon and the littler ones in the 3rd row. With 6 rather than 7 in the car, I honestly find the boot big enough without a roof box. Different if you're planning to take the nanny with you for w/e breaks though.
X5 Diesel with 7 seats + other toys (sat nav leather seats etc) is just short of £50k. A new Volvo would be less.
One more thing; access to the 3rd row is v. easy in the Volvo, because the middle seats each retract separately. The X5 has a 60/40 split, but the access is still easy as I think there is a little bit of hydraulic boost or something - it certainly felt that way - to help you tilt/lift the bench. Volvo has as standard an integral child booster in the centre of the middle row. BMW don't offer this. Mercedes does, but it's an option to pay for.
Personally I'm not keen on people carriers, but I do like the look of the Grand Voyager with its sliding doors. However for us the imbalance of the seating arrangements wouldn't work; only 2 admittedly capacious seats in the middle, then a bench at the back. If I have only 3 children in the car, I want to 3rd row out of the way sometimes tbh.
What about Merc R Class (6 seats ?)