We're lifelong New Yorkers and live in Manhattan, but my kids (ages 7, 9, 10) have been asking to do this bus tour for a while. Overall everyone had fun. We especially appreciated tour guide Diana, a real New Yorker with lots of great insight and energy.
A few caveats, in terms of expectations: 1) It's not really "hop-on, hop-off", because it can take 10-15 minutes every time you want to get back on the bus (wait on line at the stop, let people unload, let people rearrange their seats, and THEN get on the bus, hoping for a good seat. 2) We only rode two different Big Bus buses, and they were both full upstairs. I did notice the competing hop-on/hop-off bus company, and their buses were much less crowded. 3) One of our buses was full upstairs so we sat inside, but there was no A/C and no windows. Disappointing. We were able to move upstairs at the next stop.