I agree with Michael's assessment
When my kids were younger, we did the truck/camper route. As they got older, we did ditch this and started to do more tent-camping. It's easier to do this when they're older and, well, cheapskate me, likes to save a buck wherever I can as long as I still have a fun trip.
I really think kids and camping go well together. It's a lot more fun for them to be able to run around and play in the campground, burning off energy, than it is for them to be in a motel room. Even if the hotel has a pool or some other recreational area for them to play in, they typically can't "let loose" the same way they can in a campground. So I definitely lean toward saying that you should do the pop-up camper!
Of course, this means you have to be comfortable enough with towing it to do this on a long trip.
So, really, only you can answer this question but, hopefully, we've given you some things to consider.