Tricky. You can't involve your husband, because he doesn't know they are coming, right?
I think it was a bit (okay A LOT) presumptuous for them to book a room for YOU as well, without speaking to you about it. Particularly when it wasn't the place you TOLD them you were planning to stay.
I do think you should pick up the telephone and try to make "live" contact with them to see what is going on. Maybe they "booked all of our rooms" for just THEIR families, not including yours. ?
It really depends on your husband though, what to do if they did mean to have booked a room for your family as well. If he would "take their side" in something like this, then deal with it and book another room at hotel B, as close to their rooms as you can get. If he wouldn't give a second thought to any of that, but would be unhappy staying farther from the strip, then keep your own reservations at hotel A. Either way, you need to have live conversation with the other parties to let them know exactly what is going on so everyone knows who is staying where.
Family vacations can be great... but things like this always make me stress over them. Why can't people just communicate and not make decisions for everyone else? Ugh.
Sorry this is happening to your plans for a wonderful surprise for husband.. :/
ETA: my husband is a people pleaser, and would say to take a room at hotel B. I would be like you, and be miserable about it. Unfortunately, I sometimes wonder if that isn't why we sometimes find ourselves in such predicaments (me & hubby)... because they all KNOW he will sweep it under the rug and go along to get along, b/c he'd rather be with family than worry about "trivialities"... but me.. I like my comfort. He is learning though... he now will only stay at Hampton Inn when we travel, lol.