I think it makes sense that relocation will be voted on first. It is the fundamental question in all of this and is a big reason the BoG is concerned about if and when each city can build an arena.
I read that the Hansen/Ballmer binding contract was contingent on the approval of relocation. If that contingency is part of the contract and the BoG votes down relocation, then that contingency not being met would cause the contract to be null and void. (And I would expect the Seattle group would withdraw the offer anyway.) Hansen/Ballmer and the Maloofs would have to amend their contract to remove the contingency or enter into a new contract and start all over. If Hansen/Ballmer really want a team in Seattle, I don't really see a reason for them to want to change the contract to an offer to buy the Kings without relocation.
And if the owners approve relocation, then its likely they know already, at that point, that the sale will be approved, too. I would even expect, that if relocation is approved, the vote for the sale could be unanimous. Either scenario keeps the BoG from looking totally splintered, because they really never have to choose one owner over the other.
Bottom line, Sac is going to need 16 votes to block this, in my mind.