OMG YES. And thank them for being so awesome.
And tell them they were amazing, and that I've always admired them, and that I wish I could be half as awesome as they are.
It will go something like this:
Me, turning to Madeleine: I CAN'T BELIEVE WE'RE ACTUALLY MEETING SWITCHFOOT.
Me: OMG I'm so excited.
Me: OMG you guys were so awesome!
The concert was so much fun.
Madeleine: blah blah blah.
Me: I've always wanted to thank you guys for being such an inspiration through your music, you've helped me through so much by me just hearing your songs, and I'm always been so grateful and always wanted to get the chance to thank you.
The end.
Yes, I have thought this through at night when I can't sleep and the only thought on my mind is Switchfoot.