You are going to want both a wide angle and probably a telephoto if you want to get pictures on the ground. The wide angle will be good for in the basket if it's wide enough and can focus that close.
If you have never taken a balloon ride before, wear hats if either of you are tall. The burners are not that far above you and they put off some heat when the pilot sets them off. If he uses one burner it's not too bad, but if he fires both burners, it's a blast and half... and it's loud as it's basicly a controlled explosion of flame each time he pulls the cord. The hats will keep you from feeling like you are going to singe your hair.
You will be going at the speed of the wind, so you won't feel it. If you are lucky you will get some nice sunrise pictures. Get there early so you can get pictures of them setting up the balloon if you can.
And of course we expect to see some of your shots.
Mike