Choosing a good nikon lens for events?

Hi I'm going to my grandfathers birthday next month and I want to take pictures there but I don't know which lens I should buy to take nice pictures of the event. I have a Nikon D7000 and my budget is $500-$700

If you know how to operate both camera and lens properly any current Nikon lens will do. If you have a kit lens, and know how to use it… Why spend extra money on another lens just for one event?

What lenses do you already have?

Assuming you will have the opportunity to get close to most of the things you want to photograph, I would consider the 16-85mm VR lens - unless you already have the 18-105mm VR in which case I would use that.

A useful second lens is the 50mm f1.8.It is cheap, really sharp and on a DX camera acts like a 75mm portrait lens. It is very good for quite low-light work.

Another possibility if you've already got the 18-105 is to get a good flash like the SB-700 which will allow you to use bounce fill-in without getting redeye and to get more photos later into the evening and indoors. If you do get that I would recommend you practise quite a bit with it before the day.

Inside?
Outside?
Lighting conditions?
What glass do you already have?
Do you have an external flash?

Jim is partially correct about being knowledgeable about using what you have, BUT… A 70-300mm isn't a good lens if you're going to be within 20' of grandpa trying to take shots and a 10-24mm isn't good when you're 50' away.

Also, slow lenses (f/3.5-5.6) used inside will need a higher ISO (more noise), a slow shutter speed (motion blur), additional light (hot shoe flash and a diffuser), or combination of those. Depending on the lighting and the desired DOF, even a fast f/1.4 lens may need additional lighting.

In other words, if it was me and all I had was a "kit lens"… I would spend the money on a SB-700 Speedlight (~$325), a LightSphere II diffuser (~$75), and a rotating flash bracket (~$125).

If it is going to be indoors, the thing to buy, if you don't already have one, is a good flash, like the SB700. Bounce flash will solve a lot of problems.