Hopefully there won't be overly gusty sidewinds for our tandem.
No, I think it'll be more a stiff breeze than a gusty wind.
You'll have mostly-tailwind to Dunwich. The crosswind section is Dunwich to Norwich, but this section is quite well hedged-in and mostly lanes. And then headwind all the way from Norwich to Watton (mix of hedged and exposed), and to Ely (very exposed, typical big-skies, character-building Fendland section), and back home (more hedgery). I'm not expecting anyone, even tandems, to have any specific wind-related issues, excepting the into-the-wind-suffering to Ely.
Thinking through the route, the only section that might feel exposed-crosswindy is from Feltwell to Lakenheath, and the wind will be from your right, which is the preferred I think. You'll be there after 7pm, some well after that, so traffic will be light anyway. The surface is smooth and I don't recall any potholes to avoid.