Some hotels are family friendly. That is, they have a pool, maybe an arcade, a playground, things for kids to enjoy. Others may not be as kid friendly, but all hotels have other guests who expect your kids to behave themselves during their stay.
If you have a child who is involved in travel sports like hockey, basketball or soccer, you know you spend a lot of time in hotels. There are games, there are tournaments and likely the whole team (if not multiple teams) are all housed at the same hotel. That makes for a lot of kids. It's great because you get to hang out with the other parents, the kids get to hang out with their friends and teammates, but there should be limits placed on what the kids can do in and around the hotel.
For instance, no other guest appreciates a gang of kids running down hallways hollering at the top of their lungs. If you don't let your kids run around like that at home, why are they doing it at a hotel? Another thing that ticks off other guests is that the quiet times aren't upheld. Just because you're away from home doesnt mean you can act out at all times of the day or night.
Being in a hotel is a freedom, parents can go to the restaurant or bar while the kids go in the pool, but this too is tricky as kids should always be supervised around water, no matter their age. Even if parents take turns on pool duty, it's better than no supervision at all. Ideally, the kids should behave properly in the pool area which means no running, no diving into shallow water and observing the pool rules. Same goes for the gym or fitness center if the hotel has one. This is for all guests to use, and if your child has a legitimate reason to be there, supervised then that's great, but having a bunch of kids hanging out in the gym annoying other guests is a no no.
For the most part, kids and hotels are a great mix, and families are observant of the rules, the kids are polite and quiet and all is well, it's when they area allowed to run amok that the problems arise. No one wants to be the one getting kicked out of a hotel so abide by the rules for fun for all.