How can I get toddlers to community lots?

You can’t I’m afraid. Toddlers will not come to play parks with their families unless the player invites them.
Once your sim knows the toddler they can invite them, but they won’t show up on their own initiative.

(Reads original post title)

lol, Since they're not coming out, I had Noelle Lothario (Formerly Rocca) go meet a household I stitched together in manage worlds (They're all back with their parents now (sort of).
https://i.imgur.com/hxYWnWe.jpg

Noelle went to visit Elderly Vatore (Calebs wife, can't remember her name) and met Lacy Goth, Tracey Vatore (Caleb's daughter), Mae Pancakes, Luke Straud and Ember Lothario (who she already knew, her daughter with Janessa Lothario - grand daughter to Don- who got taken away by sim social services but was adopted by the El Khouri family - thanks MCC!)

https://i.imgur.com/bI5GrL9.jpg
also Tina Goth (Lacy's twin) and Olive Piper, the little exhibitionist!

All the toddlers have been moved back home now and Tracey and her Mam are back in Caleb's house. It looked like Ariana Lothario-Goth (Noelle's daughter with Toby Goth) would only get to meet her half sister. Now I can throw a toddler playdate! Yay!

I use LittleMsSam's "More visitors" custom lot trait.

You can either have the parent make the rounds of the neighborhoods and do a quick intro to other toddlers and then move onto the next one so you'll have the ability to invite them to lots.

If you're not opposed to mods, there is one by Weerbesu called "Invite Any Guests". This allows you to invite any sim to your social events whether you know them or not. So you can invite any toddlers over for playdates and invite them over for a house party or to any other social event. I've found an easy way to introduce a group of toddlers quickly too without having to do repeated "talk to strangers" interactions between the various toddlers and without the sad moodlets that go along with talking to strangers. Turn on a stereo or speaker, have your toddler start dancing and then click on the other toddlers once they enter the lot to invite them to dance with your toddler. They'll all get relationship points while dancing together and you can basically get one big group intro among all the toddlers.