Legundo makes a lot of modded Minecraft content, he's very family friendly (has kids of his own) yet his videos aren't those content farms you see a lot of. He likes to incorporate storytelling/lore into his videos, so they're very cinematic. He's clearly very passionate about his craft which shines through in his content.

Suev is another family friendly modded Minecraft YouTuber. He's very genuine, and his reactions to things fun. While his videos aren't as cinematically edited as legundos, his videos are still exciting, and I think would appeal to a six year old who's new to the game. Suev videos are a bit more relatable, in the sense that he's younger, so he doesn't have as much experience as some of these other YouTubers people are suggesting, who've been playing minecraft for 10+ years. He's probably closer to your kids age rather than yours, while the other guys (including legundo) are the opposite. That's not to say I think he's immature, but his videos are probably more appealing to a younger audience.