Adirondack/Fingerlakes OR Upper Peninsula Michigan

I like the UP fine, but should point out that scenery tends to be at or close to the shores. Inland you find some nice lakes in spots, too, especially western UP, but the bulk of inland eastern UP is low, swampy, flat and dull. Just FYI. Still, plenty to enjoy in the UP as a whole!

Mountain biking, or road biking? Road biking in the Adirondacks puts you on busy, narrow roads. I know there are mountain biking areas but since I don't do that I have no specific information for you.
Hiking can be anything from flat day hikes to one or more of the High Peaks. But the High Peaks have gotten very, VERY busy especially on the weekends. There are numerous smaller peaks with good views though.
NY State is in the process of planning a multi-use trail from Tupper Lake to Lake Placid following an old rail bed. But that's a few years down the road.
Our favorite cg is Rollins Pond, a no-hookup state cg. For a private cg we prefer North Pole Resorts (100 Acre Woods side.) It's in Wilmington, outside Lake Placid and close to Whiteface Mt. There's also a KOA in Wilmington but we've never stayed there.

Any one would not be bad. The character of the scenery is different in these regions, but there is plenty of it and all the activities mentioned in any of these areas. The Adirondacks tend more towards the mountainous side of things, so if hiking up (rather than hiking across) is more to your taste, that may be a better area.

Don't omit good insect repellent in any case.

I'm personally more familiar with New York than Michigan. Letchworth state park is one easy recommendation with fantastic scenery and a good bit of hiking and biking in the area, though it's arguably a bit west of the finger lakes region proper. There are many other fine options, too.

Adirondacks

I would recommend Lake Eaton CG a NYS DEC camp.
Lots of hiking in area. Camp rents kayaks and canoes