How does song length factor into ceremony music?

MBeezKneez

I want to play "Halo" by Beyonce for the processional/aisle walk. The problem is, the song is 4 minutes, 19 seconds long...and my walk is relatively short. 

My music is DIY with an ipod and my brother's PA equipment (and he's in the wedding party, so he's not going to be able to change the music), so...how would I make this work? Have it start playing before I walk, and let it go for a bit, and then walk after a certain point? Mix it so it fades away after a certain amount of time?

I don't want to bore my guests to tears but that song puts ME in tears because it is so freaking gorgeous, and I really want to walk to it.

Any ideas?

ETA: I'm also thinking of using this cover of it instead of the original: http://youtu.be/ACU7tgqvqbk So maybe it wouldn't be so terrible to have it start while people are still getting settled, and then walk at a certain point...or something. 

TogetherPerfect

We are thinking about 18th Floor Balcony by Blue October and it is over 4 minutes long as well. I think we decided to have it start when the grandparents and parents walk out to their seats, then have it playing for the bridal party to walk down. There's a certain part of the song that I want to start walking out to (a beautiful instrumental part), and then we will just pick a good time to have it fade out.