My daughter plays with our two neighbor kids all the time and we probably did it at 3.5.
She’s my third. Now she’s 4. If someone else invited her to a drop off play date I probably would. If they invited her to a not drop off play date she probably wouldn’t be able to go.

I don’t have time for that. Also she goes to preschool part time and my parents watch her part time while I work and my mom actually takes her to play with a neighbor friend the same age by their house too.
She plays with the above mentioned neighbor kids almost daily and then she is also friends with younger siblings of her older brothers friends so she sees those kids on a regular basis too. No real play dates so to speak but lots of playing with kids, particularly as a pack during little league games lately.