Roll20 is another mainstay for online ttrpgs. But you could always go down a rabbit hole of 1 player games you can find at RPGDrivethru. Your older kid sounds like they're right around the age to begin their rpg adventures if interested too.
@Betsy do you know of any adventures I could do with her?
My husband has been talking about something we can play with our 5 year old to teach him dnd. I'll ask him when we're both awake and get back to you. I also know my 5 year old loves making minis on Hero Forge. So letting him make a character for the game we're going to start has been fun.
I love DND but it's been a challenge with my one year old this last year, and my old online game fell apart. Roll 20 and discord really worked well for us though
My friend group usually plays through roll 20. As of now, only one tiny human from the bunch, sp we play after her bedtime
So my husband says Roll20 is the best way to play online with others. He was prepping a Pathfinder game for us to play at home with our older son. He also found a Tales of Zaidia game he wanted to play because our son likes that Netflix show.
@Elizabeth I dont know if your LO is in to my little pony, but they make a MLP roleplaying system. My brother was planning on running a game sometime. I could see if he would be up for running it online and including you guys if you're interested
My cousin is a DM for online games. I can connect you with him if you'd like to check it out, I'm not sure what he has going on right now. I took a break after the last campaign we finished. Dndbeyond.com is where his games are hosted. He has a 2yo son so he understands kid aggro and whatnot.