If you are staying in the main campgrounds, I wouldn’t count on any access to power. Some charters do provide charging stations.

Finding power can be an issue but you can usually find somewhere to charge your stuff.
Most of the main campgrounds are at schools and a lot of the time the schools will be open, or there are outlets on the exterior of the building.
I recommend bringing a power strip because a lot of the time the outlets you find are taken.

I cannot speak for every RV owner but if someone shows up at my motorhome with a medical device that needs charging I will start up the generator and let you use the exterior outlet. I think that most people would do the same and a lot of townspeople will let you use the exterior outlets at their homes. If you are with a charter they will almost certainly have a generator for charging phones and you could use that.

Don’t sweat it. I have been camping with the plebe’s for 7 years straight. There is always power, you will just need to do a little hunting. Could be in a building, could be on the exterior of a building. The biggest issue is typically when you find it, there is a rats nest other devices already connected. The smartest thing to do is bring a short 4 or 5 port power strip with you so you can patch in. People will appreciate the open outlets as well. I have often left mine out there over night so people can stay plugged in and it has never been stolen. Best part of RAGBRAI is the community.