rsnyc,
A wired connection is always better when available. Voip is well within wireless abilities to deliver. Let us know your results.
PS
brush up on the QOS settings. That's the first thing you will need to set up if you want to manage users internet activity over the lan. If your internet is only used for voip you may not need to set up QOS.
You might hear someone in the house complaining "ANYONE DOWNLOADING ANYTHING OFF BIT TORRENT, OR WATCHING YOU TUBE, TURN IT OFF, I'M ON THE PHONE!!!"