I think the Kings need a solid Third Line Center that can produce, more than a Top 4 Defender. Dowd/Kempe/Shore are just not third line center material, if you ask me.
Maybe that's where the money should go.
They'll likely add a veteran backup goalie in the range of $1.5M or less who can appear in 25 or so games.
Depending on how the expansion draft plays out and what trades are made, they very may be looking to sign a UFA dman. That's where an option like Del Zotto could be a good one, as he is used to logging 20+ minutes and playing in all situations.
Then up front there are a few needs that could be addressed. Like you suggested, getting stronger down the middle seems like a must if they wish to contend against the depth of their division rivals. Then they also need to add some scoring support on the top lines, as Kopitar doesn't appear to have any capable wingers to play with looking at the lineup as it is right now.
With the two biggest hurdles taken care of, I imagine Blake will still be active and we'll see some more changes to the lineup in the upcoming months. They're guaranteed to lose somebody at the expansion draft, and they could be losing more than just one player if they work out some agreement with Vegas.
I bet they'll also still be looking to add some more free agent prospects in addition to loading up the prospect pool in the upcoming draft.