Canoe instructor Steve Wadley, 36, and his partner Joanna Gilbert, 35, will undertake the sponsored canoe marathon on November 24.
"We hope to restore and refurbish the buildings to make them a meeting place," said Steve, who works at a Wyeside canoe and activity centre.
"We will be starting at Glasbury, which is the highest navigable point we can reach, and will go all the way down to Chepstow. I reckon that's about 100 miles plus.
"The cost of the building work is about £465,000, and when finished it will be a centre for conferences and all sorts of public use."
Steve and Joanna are hoping to take pictures of their adventure so that they can give slide shows afterwards.
They are hoping for good weather and, of course, sponsors. Anyone who thinks they may be able to help can contact Steve on 01600 772294 or 07974 769546.