alt Hacker NewsI don't know if apple will allow you to do it on an ipad, but even very young kids can learn to use something like newpipe or yt-dlp which can download videos and removes youtube's ads. If nothing else you could download ad-free videos and copy them to a device so there's a massive library of safe media you've vetted and wont have to worry about.
I use YouTube ReVanced and NewPipe on my own snartphones but I have not figured out of how block ads on the iPad (it does use DNS-based blocking via Unbound blocklists on OPNsense), she just got the iPad for a few days. On our smartphones, the children are the primary users of YouTube (on STB too, there we use SmartTube). Even YouTube Premium Family I had was primarily for my children. However they increased the subscription costs and went after people who set a different country than where they were located (I used India and paid 2 EUR a month). Now I am forced to pay the price if The Netherlands which is an illegal geolock since I should be allowed to define I am from elsewhere in EU (because I might be from Romania, living in The Netherlands).