People do it in places like Orlando all the time. Tpical hotel rooms in Orlando have 2 double (or queen) beds. Rarely an issue.
Not a good idea in Europe. A typical hotel might have economy sized rooms. Rooms which only have one bed and which don't even have room for a cot or even an air mattress. Pl customers with 3 guests might have to pay $$$ to upgrade their room or could be completely out of luck.