The 2 Iowa campgrounds are within 45 minutes to an hour of each other, so that is probably an either or choice, but both are good choices.
Indiana Dunes area outside Gary Indiana has 2 nice campgrounds as well. It can be a bit confusing as one is a state park the other a national park. We stayed at the national park CG a few years ago. It was very resonably priced when using our Golden Age (senior) pass. It does, however, not have hook ups. If you want electric, etc, I think the state park has those.
After Gary, I would part ways with I-80 and take I-94 into Michigan. By then I-80 will be the Indiana toll road.
As you enter southern Michigan, there are several decent state park campgrounds. Fort Custer, outside Battle Creek is one of them. It's about 3 hours or so to Port Huron from there.
I'd suggest picking up I-69 east of Battle Creek/Kalamazoo. Avoid the Detroit metro area. The roads are absolutely horrid, potholes big enough to swalow your RV. Much of southern Michigan has construction in places, but most of it is manageable if you allow a bit of extra time. We just keep in mind much overdue "short term pain for long term gain."
Your closest MI state park to Port Huron will probably be Metamora (less that 10 miles south of I-69, but still an hour+ to Port Huron). Have not been there, but in general MI state parks are pretty decent. Many have had a refresh in the last year or two from all that Covid funding. The
MI DNR reservation site (
https://midnrreservations.com/) is pretty easy to use; not nearly as glitchy as many others.
We actutally travelled from Michigan to Utah and back to Michigan. Once on I-80, the weather was no issue. Dry, no rain or snow on that segment. We spend a month touring the Utah Mighty 5 and other national parks along the Colorado/Utah border and 4 Corners area.
We did reroute on our return trip due to 8" of snow over the higher elevation pass across the Rockies as we had planned to head back toward Denver. That was very early May though. I can't speak for today. Coming from Vegas you aren't likely to be in that area (Black Canyon of the Gunnison) anyhow.
Once you cross from Port Huron into Canada, the QEW/401/403 is a pretty easy, even somewhat boring drive. It's been a while, but in my college days I made the Michigan to Boston trip on a regular basis. If you are Montreal bound, I don't know if you plan to cross back in to the US at all or not. If you do, be warned that for some reason the crossing at BuffaloNY was always slower with grumpier agents. I'd recomend the Queenston/Lewiston bridge crossing north of Niagra Falls. That one always seemed faster and smoother (except once, when it was Canada's Independence Day weekend, just before our 4th of July. Be forewarned and plan accordingly.)
Enjoy your trip.
