So the general plan is Vaporeon will pass def boosts over to Espeon, who will then calm mind boosts and hopefully sweep with stored power. Obviously Vaporeon could potentially pass it elsewhere, Sylveon a good recipient, but Espeon is the focus.
Sylveon does what it does, get one calm mind boost ideally then just fire off hyper voice until it drops generally.
Jolteon again, firing off thunderbolt, or switching for momentum.
Leafeon idea is to SD, survive any SE special attacks with the sash, and assuming no priority, proceed to do as much damage as it can, probably the weakest build out of the team IMO.