best lens choice for shooting small reunion tonight

Hi, I originally posted in the wrong forum. I needed some advice on lens choice for shooting a small family reunion. I was asked to fill in on short notice. My normal "thing" is macro and pets. I feel little overwhelmed, but am eager to take on this opportunity.

The event is from 7:15 to 8:15 at a country club. Inside venue with a lot of natural light and some fluorescent lighting. Most of my shooting experience has been with the 30d. I recently bought a 5d. I intend to shoot both camera's. I considered renting a 24-70L, but am hesitant. I thought I would load the 85 on the 5d, 17-40 on my 30d, and have on hand my 50, 70-200L. Here are my questions:

1. Any suggestions as to whether that set up will work?
2. Should I use flash? (not much experience here, always shoot natural light)
3. When is the best time to assemble folks for groups? (requested)
4. I planned on shooting with an aperture of 1.8-4 and AV mode instead of M, and iso around 400 as opposed to 100 if its darker. Is this the wisest choice for the candids?

Yeah, I'm anxious, if you can't tell. If I do well, then it could turn into something more permanent. I appreciate any advice.

Depends what you're trying to capture at the reunion really. Are you trying for candids, formal groups, shots of a few people chatting, etc?

I would use a standard zoom with flash pointed at the ceiling. 17-40 at the long end would work. You don't list a flash in your gear so that cuts that out. You could use on camera flash as a bit of fill maybe.

Don't use F1.8 unless you just want the tip of someones nose in focus. For small groups F4 will be ok, for large groups F8. You can't do that without flash though. Use ISO1600 if you need it, and if you don't have a flash you will.

Thanks Tim, I did use a flash. They wanted some portraits, group shots (large and small) and candid as well. Of course the night went crazy as the air conditioner was broken (100+) outside. Lets just say I have all the respect in the world for those professionals that do this type of photography all the time. I did this last minute for a friend, and well, flowers and bugs are much more cooperative! LOL Not sure that I want this to be a recurring thing unless I do some lens rearranging and a heck of a lot more practice.