Whichever way you do it, it will not be possible to avoid some damage to the boards.
The thing to use is a small bolster chisel, often called an electricians chisel.
Hammer the chisel in between the boards and break the tongue off the boards every few inches.......then lever up. If you do it carefully there will be just the marks where the bolster levered against the boards.
DIY how to tutorial projects and guides - Did you know we have a DIY Projects section? Well, if no, then we certainly do! Within this area of our site have literally hundreds of how-to guides and tutorials that cover a huge range of home improvement tasks. Each page also comes with pictures and a video to make completing those jobs even easier!