We use Motorola 250 FSR radios in the parks and they work great.
When choosing FRS radios be sure to get the privacy codes also known as coded squelch. With them finding a combination of channel and code that is fairly quiet is possible.
Using some radio etiquette helps everyone. When calling someone to start an exchange say who you are calling and who you are.
You off the ride yet? vs.
Bob, Sally here, are you off Space Mountain yet?
In the first Bob doesnt know he is being called or who called. In the second Bob knows the call is for him and to reply to Sally. Anyone else on the same channel / code knows it isnt their family.
Turning them off in shows and quite rides keeps you from getting a disturbing call on the channel / code you are using.