[travelin texans]

IMHO, with 3 young'uns on board bigger is better!!
If you've found what you think will work for you don't let others change your mind.
As to being newbies, we were all there at one time & most of us are still at it, in our case some 40 years later, fulltiming the last 10+ years.
Will you make mistakes? HELL YES you're human, but learn from them. Will it be an experience? HELL YES, one you'll never forget.
One bit if advice, get plenty of truck, large 5th wheels are heavy so don't let some salesman talk you into something til YOU have done the research. With a 5er that size a crew cab diesel dually is your best option as far as power, payload & room for a family with 3 car seats. We've hauled grandkids a lot & the best option in the truck was the rear seat entertainment center, tv, headphones, they would ride all day & all we ever heard was "movies over" which meant put in another.
My recommendation is buy what you want with a big truck, hit the road & don't look back! Enjoy this big beautiful country!