My mum has a 58 plate Peugeot 807 - I think they paid about £10k for it, with about 20k on the clock
It's LUSH - it has 6 seats in the back that can all come out, so we just use the 3 middle ones (which should be ok for you with 3) and that leaves a HUGE boot space behind
They have sliding doors which is fab for getting kids in and out in car parks, and its pretty economical, although theirs is a petrol
If I was going to get a large MPV I'd get one of those