[X] Gwarg could ruin their surprise if they don't get rid of him. It'll mess up their schedule, but they need to track him down and finish him off. It's still daytime, so hopefully he couldn't have gone too far.
[X] Buffy plans an all out assault on Wolfram and Hart's assassins in LA. If this war's escalation is inevitable, better to strike first, and Congressman Gold should at least be able to keep the LA authorities out of it.
[X] With his Shadowurm dead Gwarg isn't much of a threat anyway, and a guy that lives in a sewer probably doesn't play very well with others. There are a lot of assassins to deal with, better to not get bogged down in a sewer.