As an alternative to VOIP, running your own PBX or making an adult put up with phone calls at home, you can buy a prepaid cell phone. Tracfone
http://www.tracfone.com has very reasonable rates and extremely inexpensive phones. These include voice mail that can be checked from any phone, so the message can be changed remotely.
Right now I see on their site a phone that comes with 140 minutes that lasts for 90 days for $30. A card for another hour and another 90 days costs $20, so for $50 it would get you well through the championship.
And it's not like anyone will actually have conversations on the phone and consume any of the minutes... people would just call in to hear the voice message, which doesn't cost anything. When you want to manage the voice mail you can call from another phone and it won't cost anything.
Good luck,
~Phil