This should do what you're looking for.
Code:
local npcid = ######
function BossStarter_Gossip(Unit, event, player)
Unit:GossipCreateMenu(0, player, 0)
Unit:SendChatMessage(12, 0, "Are you ready to attack?")
Unit:GossipMenuAddItem(0, "FOR THE ALLIANCE", 1, 0)
Unit:GossipSendMenu(player)
end
function BossStarter_Select(Unit, event, player, id, intid, code)
if(intid == 1) then
Unit:ModifyWalkSpeed(8)
Unit:MoveTo(3243, 534, 59.2, 1.587267)
player:GossipComplete()
end
end
RegisterUnitGossipEvent(npcid, 1, "BossStarter_Gossip")
RegisterUnitGossipEvent(npcid, 2, "BossStarter_Select")
Just replace the red "#" with the id of the npc.