I have a CPAP and will be taking a couple of batteries, as I understand there is no electricity at all available at the campsite. But are there any charging stations where these batteries can recharge during the day?

If camping they have few sites with 5 amp connections for medical purposes

I am sure you can charge your machine there just ask.

There are handicap sites at campground with electric.

There are no public charging stations. I am sure they will let you charge at the ranger station (that is closed at times). We brought a solar charger and an emergency car starter which gave us several charges.

Maybe the Souvenir shop.

Try the ranger station or the campstore. I'm sure they'd let you.

You may can ask a park rangers if you can charge them

No