So I took a couple to Three Lakes for their honeymoon for a 3 night stay. The first two nights I had them at the campground where they used the tents for free. I decided to let their last night be at a hotel. When I checked in, they ended up billing me 2 more times right away, as if I stayed there for their whole vacation.

Is this a game bug? What happens if you stayed at a cheap hotel the first night and switched to an expensive one the next night? Will it charge you for 2 expensive nights?

Their honeymoon was suppose to be within a budget, so I guess they ended up spending the money they needed to build a room for their first kid xD

If i remember it correctly they charge you every night at 12:00am.
So if you get to the hotel by like 9:00pm, Check-in, pass 12:00am. Bills you for 1 night.
So if you pass another night, they'll charge you for another night.

Or maybe it's a game bug.. I dunno.. Maybe you should try patching your game. Game Bugs is annoying =(