For minivans, some Toyota Siennas have AWD and are probably the most spacious option.
For mid-sized SUV's, the Honda Pilot is probably the most common vehicle that will fit your criteria. They all seat 7 and I think most have awd. You can almost get a new base awd Pilot for your budget.
The Toyota Highlander fills the same niche as the Pilot and all have awd and 7-8 passenger capacity. You actually could get a new one for your budget, although it would come with the less powerful 4 cylinder engine option.
The Mazda CX-9 is also 7 passenger, is powerful, and will probably have the best driving feel to it.
In my opinion, these are the "smart money" options given a $20k-30k budget; awd and 7 passengers. These have the best combination of fuel economy, reliability and depreciation in the segment.