I totally vote for a Class C rather than B. You'll have a lot more room, more storage and better sleeping arrangements for the 2 children.
Starting out in a tent is fine but it's completely different than an RV and might just turn you off completely. It's a lot more work and less comfortable, especially if it rains.
We did start off in tents 50 years ago and went to a pop-up (which might also be good for you to start), a couple small travel trailers, a 5th wheel for full-timing for 8 years, and the last 10 years full-timing in a Class A. Can you tell we thoroughly enjoy the outdoors?
Best of luck to you and don't be hesitant. It's a learning curve and anyone in campgrounds will be glad to help if you have problems.
