A boat trip to see the sights from a warm and cosy covered boat.
Pancakes are a must. For breakfast?
Probably too cold for vondelpark.
If you want to see Ann Frank House you need to look on website for details of how to get hold of tickets. They are released a few weeks before. I keep missing it. It's only small and young kids will be free.
I don't think you have to do kid friendly things constantly. If you only have 24 hours then you need to see the city not go to a science museum.
Ooh take them to The rubber duck shop in the 9 streets district. Pricey but cute.
Also you really need to see the 9 streets. It's lovely. There's a fabby shop selling chips. They are the best. I will try and find it. Bit cold to eat outside and it's takeaway.
For food try foodhallen. It's amazing and you'd be bound to find something to please dc.
Or go for rijstafel (Indonesian feast) in 9 streets and give dc rice or spring rolls if they'd eat that kind of thing. It's a very Dutch thing to do.
If it were warmer you could hire a bike with a big clog shaped trolley for dc to sit in. Personally I'd find cycling around Amsterdam terrifying.
We went for 24H this summer and had a lovely time. I wanted to go to van gogh but too little time so we settled for wandering and a boat trip, eating, vondelpark and the museum of our Lord in the attic which I'd missed the previous visit. That's very good for dc as they have a child friendly commentary. My 9yo and 12yo loved swiping the child sign to hear the commentary. We swiped the adult one. Yours might be too young.