Hey Cottage Girl - Now also known also as "Fudgy" (since you are visiting Mac Island),
With a great day today up here, you should be OK via line of sight and google maps will point you to the right areas to traverse from Burt Lake to Mullet Lake and to the Cheboygan river.
Just don't spend too much time at the Hackmatak Inn and Pier thritysomthing bars on the Cheboygan river on your way.

What kind of boat are you making this trip on? I've wanted to make that trip for years but just don't have the desire to trailer from Douglas Lake to Crooked River and then back.