I loved Amsterdam but didn't go with kids. I agree about the canal trip.
The diamond exhibition we went too wasn't great, quite interesting but from what I remember, it was quite high up with the workbenches and such so depends on how old the children were as to whether they'd be able to see anything or be interested. We just popped in on the way to the Bols Museum (great but obviously not suitable for children).
I enjoyed the Zoo (Artis Zoo I think it's called), quite a big zoo so you could have a good day out there.
Ann Frank's house was a must for me. I'd say it'd depend on the age of the children though as it's quite a bit of walking through narrow rooms and passageways and up and down stairs and quite a lot to look at and read and some video too. Could be difficult with very young ones, especially as it's a place which deserves peace and reflection. There may well be a long queue too. We went first thing and the queue was still very long.
Pancake and waffle houses are a must too!
There used to be a floating Chinese restaurant, not sure if that is still there but could be an experience, heard it was quite pricy though. We went to a Chinese restaurant but it overlooked the main red light district, quite interesting to see it all come to "life" but, not for kids.
There's a Science Centre:
https://www.e-nemo.nl/en/
Nice to just wander too, round the canals and squares and markets and marvel at the sheer amount of bikes, there are some beautiful buildings. There may be some more family orientated walking tours, maybe even ones on bikes too! Got to be places to hire bicycles too to get around yourselves.
When we were there there was a fairground set up in Dam Square, near our hotel, so maybe check if anything like that is on.
Wouldn't be my choice to go with children but sure there are other suitable things for them to do.