My port is full, and I'm stumped

So today I tried to send off a grown up child to travel. But the thing I didn't realize until today is that ports can get full, my island has had so many kids and none of them have been sent away. I know they travel by Streetpass, but in my near decade of playing this game on and off I have never, ever been able to give or receive a traveller. I've never encountered another person with a copy of the game out in public, let alone while we're mutually carrying Streetpass enabled 3DSes. I'm planning to turn off babies on my island as I've seen that as basically the only solution, but I have multiple kids still in the process of growing up. Will they be trapped at their parents' house indefinitely? I know I could clear up apartment space, but I have maximum residents and really don't want to delete anybody, so I'm saving that as a last resort. Feeling frustrated.