Go with aluminum anodes, they work in both fresh and saltwater.
VC17 does not work well in salt water and other bottom paints do not adhere to VC 17. We're planning a similar trip out the St Lawrence from Lake Ontario. Last spring I bit the bullet and removed the VC17. A tiresome job.
Removing the VC17 only and not the underlying barrier coat can only be accomplished by sanding with fairly aggressive sandpaper. In areas where the VC17 is thin and smooth, 80 grit will suffice. In areas where it was built up a more aggressive sandpaper was needed, we used a 36 grit on an random orbital sander attached to a dust collection system. VC17 is essentially a solid copper coating. In areas where the copper has built up, you are removing copper not paint.
We tried various solvents, Acetone, Denatured Alcohol, Xylene, and a few proprietary solvents from different manufacturers with disappointing results. They do work in tight spaces around through hull fittings etc, but mostly they just smear the paint around.
Some have used citrus based paint removers and claimed success. I tried a soy based remover and it just smeared the paint around. It might have worked better if I had tried to remove the barrier coat too, but I wanted to leave the barrier coat as intact as possible.
Sanding left the barrier coat fairly thin in spots, so I added 2 more coats.
Good Luck. If you go with the sanding option, start early. I found it slow going.