I haven't seen a computer station with a protocol that only uses IPV6, sometime IPV4 only but the default windows setting is IPV6 and IPV4 enabled on most devices, Multicast using IPV4 is the best option when announcing your game across local sub-net.
Just don't broadcast your created game 60 times a second : - D to not disrupt and flood other connected devices within the sub-net
and stop broadcasting if a certain condition is met E.g: if all players are connected, your last broadcast maybe saying the game is FULL or STARTED.
I broadcast my game every 256ms which 4 times a second and it is still seamless ^_^y