My colleages and I had a great time rafting! It took about 4hrs to get to the rafting area, lunch was provided, and then we spent 2+hrs on the water, then made our way back to Kathmandu.
We hit some class 2 and 3 rapids that was perfect for moderately active adults with no experience.
There is not a vehicle that stays with you while rafting but you can secure your items at the boat launch location and they have a "drybox" you can put your items like cellphones, wallets, or passports in if you want to keep them close.
I would recommend water shoes of some sort.. We had to walk over a few sections of rocks and i really wished i had been better prepared and that i was not barefoot.
At the end there is a changing room so you can change into a dry clothes, but you need to bring your own towel.
The transportation part of the trip was the most concerning part to me, but they took care of us and had peope waiting at each stop ready to greet us and make sure we were headed the right direction. All things considered, this was a great trip and i would recommend it to friends!