I want to go on adventures with my kid. I'm not an experienced GM so something or things that are relatively simple to run and also levelled for a 5 or 6 year old. Could be campaigns or one pages
I know this is an old post, but I will give a +1 to Hero Kids for a few reasons:
There's like 4 stats and all you need is a bunch of D6.
The character sheets fit on an index card and are easy enough for a 6 year old to grasp everything on it.
If you want to run their setting, tons of info is provided with quest seeds and pre-made adventures, and it is super easy to adapt to a different setting, or even totally different genre, because of how simple the stats are.
It has a great monster compendium, with tons of fantasy monsters, with notes on balancing encounters.
If you want to get creative and make totally custom monsters, the information included on balancing gives you all the tools to do that.
The PDF bundle on DriveThruRPG is like $20 for the PDFs of most of the adventures, the core book, the monster compendium, and the gazetteer, all of which are great.
I'm running an ongoing campaign with a 6 year old, a 7.5 year old and my 16 year old sister. We had a 3 hour session last time, and the ADHD 6 year old was there for the whole thing (with a couple 5 minute breaks).
If you have any questions about it let me know. I'm not a super experienced GM. I've only run Hero Kids and Genesys, with being a GM in Hero Kids being my intro to TTRPGs.