AppleTVs create a chatty alternate WiFi network

They are likely packets for Airplay, since that works over an Ad-Hoc Wireless network

Reference - https://en.wikipedia.org/wiki/AirPlay

These look to be AirPlay advertisements.

When I look at the packets in Wireshark, they are unencrypted and contain IPv6 multicast messages advertising airplay. They also contain data on the type of device, device capabilities, and who knows what other data.

At the very least, it does not appear to contain the AppleID used in plain text, so there's a plus, but I can't guarantee it's not hidden/encoded somewhere else.