Tom, I used to live up there, you need a wide tired mountain bike. its heinous, loose sand and loose gravel and pretty marginal dirt roads.
I'd try it on 700x 37s underinflated to 45 PSI, mebbe. but that's me.
that's VERY sandy country, up by Grand Marais and east.
the UP's "unimproved" roads are beautiful,
but if you're on a trike and a 'road bike' pulling a trailer, best go the Paradise to Seney to Shingleton to Munising.