This is awesome and I will definitely save this for reference as there are a few 2d6 systems I want to try out, but Hero Kids is even more basic than a 2d6 system, at least as far as I understand them.
Your stat pools are basically just the number of d6 you get to roll, and you just take the higher number. Every successful hit deals 1 damage (health pools are between 1-4, 1 being like a weak minion or a spider egg or something, 4 being a leveled up hero or a boss). So higher stat just means you are basically rolling with more advantage, more chances to get a higher number, but you always only use the highest dice.
So a hero with 3 melee attack would roll 3 d6 and take the highest number, and that is their attack roll. If they are attacking a creature with 1 defense, the GM would roll 1 d6 - if the attackers highest dice is equal to or higher than the defenders dice, the attack hits and the target takes 1 damage. Otherwise nothing happens.
I think the best way to convert something like 5e stat blocks into this would be to just say - is this monster supposed to be easy, medium, or hard - and then just copy a stat block from a hero kids monster that is similar to what you want. There is a pretty good monster compendium for hero kids so for a lot of creatures I can just use those directly.
I'm less concerned about copying stat blocks directly than I am about just having good narrative / story content, like NPCs and locations. Having never read any other RPG content besides Hero Kids (and perusing a D&D Players handbook a bit) I don't know how much of the adventures are story content that works everywhere vs just "This place has monsters with these stat blocks" that is D&D specific or requires conversion.
I didn't realize that DnD Beyond had free adventures, so I will definitely check that out, and that will probably give me the information I need on whether or not I'd like to spend money on other 5e adventures.
If that's for a whole pie that's dirt cheap. If that's for a slice then that's some expensive pie.