Sochi in May is great. Locals say it's the perfect time of year: you can still ski, and then go down and swim in the sea. A request to potential organizers: please announce at least approximate dates for the event. My superiors are pressuring me, demanding that I decide on my vacation by November 23rd.
Regardless of the location, the CIS event usually takes place around April 30th to May 7th.
Added 3 hours 49 minutes ago
Regarding logistics, here is a list of cities from which the low-cost airline "Pobeda" offers direct flights to Sochi: