In most places, the minimum age to check in is 21. When booking reservations online, make sure you are booking the correct hotel and location. If the web site gives a phone number, write it down and call after you book to verify your reservation. If just one room in your hotel has a strip view, only one reservation can get that room. Most hotels drop reservations a few days before the check-in date if you do not provide a deposit or credit card number.
Most hotels accept a maximum of five people in a room with two queen beds and a roll-away.
Some hotels may charge for each guest beyond two and for a roll-away. Do not try to cram the entire family tree into the room. This is unfair to housekeeping and crowded for you, too. If your reservation was botched, it was NOT the front desk clerk's fault. He only checks you in.