available light lens for DX indoors?

Hi, I just got a 17-55 f/2.8, and am finding that it generally is not fast enough for high quality pictures that don't have me bumping against ISO 3200 all the time on my D5000. I'm mostly interested in portraits of my kids.

I'm thinking of exchanging it for something else. I've got the 18-105, the 35 f/1.8, the 70-300 VR, and an SB-600 flash. I find that I get pretty good pictures using the SB-600 and one of the zooms.

But I'd like to get something besides the 35 f/1.8 for available light photos. Here are some options I'm considering, in order of preference:

50 f/1.8G - will I get perspective distortion?
85 f/1.8G - too long for indoors?

Sigma 17-50 f/2.8 OS - I think I'm getting shaking blur, so OS will be a nice plus. It's also a lot cheaper.
17-55 f/2.8 - just keep it

Any thoughts?

Thanks!