Good question. I'll go on a tangent to answer it.
At the beginning of Lord of the Rings (no seriously, read on), Bilbo thanks many hobbit families for coming to his 110th birthday. He mentions the Proudfoot family, and calls them the "Proudfoots". He's immediately corrected when a Proudfoot yells out "ProudFEET!!"
So my answer is... it's your choice! We native speakers will understand both.
Run for a dictionary? Remember it took us English speakers over a thousand years to come up with one... :P