Photographing an indoor party?

I have a Nikon D3000 and a 50mm f/1.8 Nikkor lens. I did have an 18-200mm Tamron zoom lens, but unfortunately that had to be sent off to Tamron for repairs about a week ago. I have a tripod, but I have no external flash, just the pop-up flash on the camera.

Though I'm shooting an indoor party, it's at around noon, and my client has a good number of windows in their home for natural light, so it shouldn't be too dark.

What is the best strategy for getting the best shots possible? I'm going to take shots of the decorations and things, try and get some candid shots, and a family portrait.

I'm obviously not a professional (getting paid less than $50), but I want to do my best since I've committed to this job.

Thanks so much for any and all help!

Added (1). I must add that this party is TODAY. I know, I know. Please don't criticize me for waiting this long. I just need the best advice possible.

Regardless how little you are being paid, people have expectations of professionalism when forking over their hard earned cash. Your lens will be too long on a crop sensor for a family portrait or most inside shots unless the rooms are huge. I would suggest renting a lens and a bounce flash.