Is there a reason you aren't looking at a minivan? The Honda Odyssey is more practical and has a 3,500 lbs tow rating. Minivans have a larger passenger and cargo area with a similar exterior footprint, ride and handle more like a sedan, and are especially fit for someone with a wheelchair. In my experience, SUVs are more cumbersome to maneuver than a minivan. My wife has a Honda Odyssey and every time she or I drives a midsized SUV, she either hates it or says "it drives like it's twice as large as my van, but it's so small inside" The only SUV that didn't feel this way to me was the Acura MDX, Lexus RX (not really a midsizer), Mazda CX-9, and a Porsche Cayenne.
I have driven the Atlas, CX-9, Highlander, Pilot, 2017 Traverse, MDX, RX, Sorento, and the Porsche Cayenne. None of these are more practical than a minivan unless you need to off-road or tow over 3,500 lbs.
VW Atlas V6: This one felt the largest by far like driving a Tahoe or Suburban. I liked that the 3rd row was pretty spacious (not as spacious as a minivan still), the interior and engine noise were quiet, and the digital instument cluster was nice. I didn't like that the ride was stiff. With the stiff ride, I thought the car would handle well in turns, but it was the worst handling SUV I've driven. The engine was refined, but not powerful enough even with the V6. Just like the Tiguan, the Atlas needs to lose 300 lbs or so. MPGs are not good and I doubt it will be reliable being in its first year and it is a VW. Interior quality was not up to VW or German standards. Car reviewers seem to love this car, but I didn't see what they loved about it.
Mazda CX-9: This one is the best handling midsized SUV by far. It is also considerably smaller inside and has a super small 3rd row. I wouldn't recommend this because of your mom with the wheelchair. I don't know where you would put the wheelchair, like if you would replace the front passenger seat with a wheelchair or if you would put the wheelchair in the trunk. If you put the wheelchair in the trunk, this SUV would be fine I think. It has the nicest interior (and exterior) of any other midsized SUV. It also has had problems with the new turbo engine in its first year. It might be sorted out this year, but we don't know. It's an SUV that makes styling and driving dynamics ahead of practicality.
Toyota Highlander: This SUV is one of the better midsizers. It is the most reliable midsize. I thought it rode very well, better than all of them except for the RX, MDX, Sorento, and 2017 Traverse. The one I drove was quiet inside and materials were decent for the class. The interior is more practical than almost all the others because of the amount of storage and features. All safety features are standard on every trim.
Honda Pilot: I really like this one. It doesn't ride as well as the Highlander, but it's not bad. The interior is better quality than the Atlas and Highlander. The infotainment system is not good and there is no volume or tuning knob. It is easy to get into the 3rd row. It was one of the quieter midsizers. Driving the car, it felt much heavier than it really was, but nothing like the Atlas. The V6 makes it one of the fastest midsizers. People have had problems with the rough 9 speed transmission on the Touring and Elite trims.
Subaru Outback: I haven't driven one, but I've heard that it is super comfortable and great in the snow. Long term reliability is questionable with Subarus because of their tendancy to burn oil and blow head gaskets. I would suggest the V6 because the 2.5L is pretty slow and you are towing. Eye sight seems like it works well and it is easily accessible in the lower-mid trims. It doesn't have 3 rows if you need it, but the trunk is big.
Overall, I think the Pilot, Highlander, and Outback are your best bets. The CX-9 might also be good if you are willing to sacrifice some space and practicality. If you want the best of everything, the Honda Odyssey is definitely the way to go. Good luck and tell us what you buy!