My answer would depend on what year $5000-$7000k gets you for each vehicle model, kwim?
Your B's are all pretty young so I'm guessing you need 4 tether anchors. That could be the determining factor for which van you get, kwim?
Or if your funds allow for a short wheel base model of something, vs a long wheel base model of something else (room for a stroller, groceries, etc) that might be the determining factor, make sense??
Or if one van offered captain's chairs, and another offered a bench, you might be swayed towards one and not the other, regardless of make/model.
Assuming you can get a long wheel base Sedona with 4 top tether anchors, captain's chairs, and under 150,000kms, I'd lean towards a Sedona. (I'm just guessing those are features you'd want, if not, ignore me
)
After that I might look at the Chrysler vans, although I really do prefer seatbelts that lock manually for booster training kids... and only '07 ('08?) and newer Chrysler vans have lockable belts. (that said, it wouldn't be a deal breaker, and I know you know not to rush your kids into boosters, so this might not be a concern for you whatsoever)
So yeah, I could ramble on, but I won't. I think you probably understand what I'm trying to say...
And ya, 4 car seats! If so, I vote for
Bean.
ETA: well, it appears your oldest B is a lot older than I thought lol. Ignore the 4 TA stuff, and booster training stuff.