Haha, that's fun.
I knew of Destiny's Child, but at the time I wasn't a huge fan. Just liked one of their songs. I enjoyed the concert, but wanted Christina to come on.
I think Beyonce is so much better, outside of DC, than when she was in the group. She is a much better solo artist.
I think that was actually 2001 or so for Britney, Neptunus, because I've seen the concert film that was taped for that tour. Were you on the DVD? I think she only did one concert on the Beach, although it is possible that she was performing in multiple venues like that.
EDIT:
Hey Neptunus, you are famous!
Check out this DVD. You should buy it, and see if you see yourself.
http://en.wikipedia.org/wiki/Live_and_More!
And it was 2000 that she performed on the Beach.