The sprinter 4x4 works a lot better than you’d think, with the help of the traction control.
Honestly the best part is being able to comfortably cruise in 4x4/awd at highway speeds when it’s rainy or patches of snow etc. This is something you can’t do with a 4x4 econoline because the drivetrain will bind and the driveline vibrations will tear things apart over 45mph. The sprinter tracks so much better through standing water and stuff with the use of AWD.
Still with 3 grandkids I’d be looking at a bigger rig if you intend to take them with you much.
On a side note there are a lot of car seats/boosters in the 16-18” width. They are all tested differently though so make sure you have something certified with a lap belt only, using the car seat’s harness if that’s something you’re considering. They’re are going to have different ratings and stuff it seems. Then they’ll outgrow them in a year or two anyway haha. Good luck. I’d push for shoulder belts too for what it’s worth. Search for Mali Mish and see how they use their 170” wb sprinter with their 3 kids using a stock 3 person bench.