Tom took Finn a few weeks ago and decided it was too much for him at 22 mths. I would say no at 16 mths. It is very very very loud.
That said, Finn had a great time with the whole experience, going downtown, seeing all the people, but he did find it hard to stay still and he also wasn't a fan of having his ears covered but also didn't like the noise. They left early lol
Save it for next year.
Heather I think 4 would be fine. Just make sure you put ear protection on him. But he would get more out of it for sure.