A playdate for 6-year-old girls is much easier to organize than one for 12-year-olds. The 12yo playdate has to have an ironclad structure and organization. An adult needs to supervise every minute and fill it with pre-planned activities. Because if you let the girls fend for themselves, they’ll form cliques and start excluding somebody. That’s all that girls at this age want to do. Form cliques and exclude. I literally did nothing else between the ages of 11-13.
It’s normal and healthy but can ruin any playdate.
Six-year-olds are very low-maintenance in comparison. I released them into the wild, and they’ve been perfectly fine. No fights, no tears, no unpleasantness.