Iowa State Fair

Adventureland is typically booked months ahead of fair time.

The fairgrounds spots with electricity are tight for the most part. There's primitive spot so you would need a genny. It sis nice being on the fairgrounds other tan the fact that it is pretty much endless hills!
Try the Adventureland campground or Timberline suggested. I'm sure you will find one you like. And if you need someone to have fun with let me know, we will be out there sometime during the fair.

might also try Adventureland park campground not to far from the fairgrounds

The KOA has the most stuff to do for the kids. They have new owners and they've done a lot of good stuff out there. Just remember that the KOA is 30 miles from the fairgrounds.

Anything up in the Johnston / Polk City area around Saylorville Lake is good. Not any organized kid's stuff there, but good "nature" parks.

The RV campground at Adventureland in Altoona might be worth a look to you. You are 7 miles / 20 minutes to the fairgrounds from there.

There are also a bunch of County parks in the area with hookups. Check out the My County Parks website.

Timberline Campground in Waukee is a decent place too. You are within 10 minutes to a huge mall and lots of restaurants. It is ~14 miles / 25 minutes to the fairgrounds from there.

Dont plan on fairgound camping at this point, these fill up fast a year in advance I have heard. We stay at Timberline CG in Waukee, IA, a western suburb of Des Moines. It is about a 10 min drive to the fairground exit on I235, but beyond that traffic can be slow. Go early to beat some of it! Timberline is a fantastic family owned CG, closer in than the KOA mentioned above.

I seem to remember that you can only reserve a spot in the Fair's campground for the entire fair. We did see RV's going in and out, but no idea of what the daily turnover is and if they have a certain number of daily/short term stay sites. We stayed at the KOA and really enjoyed the Fair. We don't use RV parks for much other than a place to stay. You might look into the COE Campgrounds at Saylorville Lake. We have not stayed there, but generally find the COE campgrounds to be nice and a good deal.

The gambling casino just east of Des Moines is a good alternative too.

Saylorville State Park. Northwest side of DesMoines. Really nice.