Sidney, Nebraska (abbreviation should be NE) and Rawlins, Wyoming. Western Hills is pretty unprepossessing, but a decent spot. If its appearance puts you off, consider the surrounding terrain. :) There's not that much available in Wyoming. If Rawlins is where you need to stop, Western Hills is preferable to the KOA. We've also done the KOAs in Rock Springs (even less scenic than Rawlins) and Cheyenne. Cheyenne is nice & clean but the entire ground is graveled with round stones & would not be good for those with mobility issues. Also not many sites to fit long rigs.
Iowa State Parks are pretty decent, though bathroom standards may be somewhat uneven (it's been many years since we've camped in one of their SPs.) Most are not really all that near the interstates. On the other hand, Nebraska State Parks & "waysides" offer some pretty good options as well, especially during the week, and some of them are quite convenient to I-80. Mostly just electric hookups, but for a night that should be fine if you travel with water in your tanks. We liked Kearny State Rec. Area, outside of the town of Kearney. FYI, there is an entrance fee in addition to camping fee. Mormon Island, Windmill and several others are strung along that route. Grand Island KOA is ok for an overnight; their best feature is a little less road noise (they're about 1/2 mile from the interstate) and freshly-baked pizza which can be delivered to your site. (Pretty good pizza too.) Extra cost for the pizza, of course. :)