With split stay, sounds like we'll each get 2 sets of Magic Bands. Do we need to use the one linked to the first hotel on the first park day?
You can use either one at any time during your stay. I like to check them on the door lock since sometimes that can be glitchy but they both work for FPs and tickets.
Both sets will work for everything the whole trip. It's nice to have the second set in case someone loses theirs or they get misplaced.