We plan on using the multi-book accounting feature due to a change in functional currency. Is that a good idea?

Meaning you're going to try and use a secondary book with the new currency as your "main" book? Hmmmm admittedly it's been several years since I dealt with MB, but if I remember correctly, there are some things that really only work well in the primary book. I can't point out anything specific at the moment though..ha. And maybe whatever those things were have been fixed in the years since I last dealt with it. Either way, I'd have someone who knows MB currently thoroughly vet that plan before going forward with it.