That’s what we just did on April 29! Mostly, anyway…
We set up the laptop on a small table and ran a line from the headphone jack to an amplifier, which was in turn connected to the speakers. I think you could probably do that from any old Mp3 player too, but my husband wanted to be sure that everything was played when it was supposed to be played, so he wanted the extra control that the laptop screen offered. (We were married outside, too!)
Also, the music was one of the most important things for both of us – especially him, but for me, too – and that was why we went this route. We didn’t trust somebody else to play songs that we would enjoy, and since we had all of the music on the computer already, it was just a matter of deciding which songs we thought we’d want to hear that day. We put a friend in charge of startingn and stopping the music – an important job, since we even had our ceremony music on there! We had everything separated into clearly labelled folders (pre-ceremony, seating of mothers, bridesmaids, bride’s march, recessional, post-ceremony, reception 1, first dance, reception 2, etc…) so that there would be no confusion.
It worked wonderfully!
Good luck, and congratulations!