Seconding Sam: the Paris Pass - which is a combo of the Museum Pass and Visite Travelcard - is a vastly overpriced bundle that I wouldn't recommend for anyone. I've never figured how anyone could come close to breaking even on the thing.
The Museum Pass, augmented by carnets (booklets of 10: 14,50 €) of single-ride transit tickets, was a much, much better deal for us but you have to do the math. Make a list of what you want to see, add up the total cost of entry fees and compare that to the price of the pass
Transport ticket info:
Carnets of tickets can be shared amongst your group. My husband and I shared 1 carnet and barely used all 10 tickets (5 rides apiece) over our 6 days in Paris but we're also big walkers so covered a lot of ground on foot. And even if we'd added quite a number of attractions or activities not covered by the museum pass, we still would have come in under the cost of the Paris Pass.
Your 16 year-old will be able to access a lot of museums for free: always have his/her passport along for proof of age.