I launched a 16' open fiberglass boat for years - with a 30 and a 5 kicker, total weight was ~400 lbs before trailer, I launched with a rear-wheel drive Mazda station wagon, a front-wheel drive Rabbit and 4wd Jeep Cherokee. I never had issues on any ramps. With the Jeep, I launched off gravel beaches, and occasionally had a little too much fun.
I'd say a 2wd van will be fine except for slimy, low-tide situations, and awd would be fine on pretty much any ramp. Gravel beaches - have a plan B.