The best you can do is wire to both sides. This has to be done, and blinds chosen, such that the power location on both sides is hidden by the exact blinds you're going to use.

That said, have you pinned down the actual models you'll use? That will let you get the information that you need to wire to only one side.

Might they change the blinds in five years, so both sides should be wired anyway?

You might want to do what I do when available product models are rapidly changing: Insist to the client that this product be purchased right now, designed around, and stored. When the Sony VPH-G90 (3 tube, $35,000 projector) came out a long time ago, I insisted on having it and doing a mock setup before construction. Good thing, too: the manual was still in Jinglish and the lens-to-screen distance called out in the manual was wrong! The number they gave was from the mount center to screen... we would have been screwed had we just gone with the manual!

Ya can't beat getting the info from the actual product.