Do you need to let hotel know you're using it as a bridal party suite?

Because there's so many people in your group, I would probably let them know. If it was just a few extra people I wouldn't bother, but an extra dozen people is a lot.

I can’t imagine why. But if it would clear your conscience then go ahead and ask

I would let them know as a courtesy, but they shouldn't have any issue with it, since people aren't spending the night. You're allowed to have people up to visit you in your room.

I would definitely let them know just to cover all of your bases and like to said, to ensure there won't be any issues the day of. All hotels have different rules, so it's better to let them know now rather than later because if it is a problem, you'd still have plenty of time to book a different hotel.

I think in most cases, hotel have limits as far as how many people can sleep in a room, but I'm not sure about just having people in the room. To be safe, I would ask/tell them for piece of mind.

I’d let them know, just so they don’t raise eyebrows at all the people going by the front desk.
Maybe they’ll be extra nice to you!

You shouldn’t have to. You’ll be the only one sleeping there. But you can let them know you’ll have some people up the morning of

I think it would work in your favor to let them know. You’ll probably need some extra chairs, they may even have tall makeup chairs. In my experience they were very friendly for wedding related things. Maybe they’ll send some champagne up for you.