Two Week Pacific Northwest RV Trip

Hello,
I have never been on an RV trip before, but I am planning one with my siblings and their respective partners for next summer. In total, there will be 8 adults and 3 children. We are all very close and get along well, so we are not concerned about being in close quarters with each other for the two week trip through the Pacific Northwest that we have planned (in its early stages). We live in the San Francisco Bay Area and plan to rent an RV (size to be determined, but definitely Class C) drive east through Utah and begin our adventure in Wyoming (Yellowstone/Grand Tetons), continue north to Glacier and then west to parks in Washington and Oregon before heading back to California.
My questions are:
1) For a group of our size (8 adults, 3 small children), what size RV would you recommend for a two week journey.
2)Are there "must-see" parks you would recommend along our rout and ones that you would suggest we skip due to our limited timeframe?
3)I have estimated about $1500 pp for this trip based on RV rental, gas, foodstuffs, park entrance fees and camping fees. Does this sound reasonable for a two-week trip as described or am I way off?
4) Are there any costs that I am not accounting for that you would consider vital to my estimate?
Thanks for any advice or response.
Sincerely,
Newbie to the RV World, But Excited

Welcome to the RTA Forum!

The answer to what size of RV you'll need: As big of one as you can find!

I'm not an RV expert, but I'm not even sure you'll be able to find an RV that will sleep 11 people. At the very least, I'd recommend getting a tent, so you won't have to crawl over the top of people to get any sleep! This could be a good option for the kids anyway.

Your budget of $16,000 should be plenty for a 2 week trip.

I am almost certain there is no RV that can accomodate you all and the problem with taking a tent would be the number of seat belts available to travel legally, so I would be think you will need to be considering taking a car as well as a tent.
We don't do "must see's" as we all like different things but the interactive map on the National parks site will give you all the info you need. There are some great ones in Utah though, think Zion and Bryce as two examples.
Once you have worked out roughly how many miles you will do you can use the fuel cost calculator on the left of every page, with the RV only likely to return 10 mpg it will be a major expense, but I agree your budget looks sound.