The Amsterdam - Zürich sleeper train is operated by the Austrian Nightjet.
Only for the night trains:
https://www.nightjet.com/en/#/home
For the "whole" company, so to speak:
The second option has an app too, which I recommend.
You usually leave from Amsterdam at 20:15 and arrive in Zürich the next day at 08:05. You can also get the train only to Basel, and you'll arrive a little earlier, at 06:20.
That being said, there are quite a few options for day trains that you can split for 2 different days, with an average of roughly 3 and a half hours of train travel each day, which should be more comfortable for kids.
(Please stop zapping me all the time, now I feel like I have to give something in return. 😂)