The 30 mile route is easy for regular riders and challenging for non-riders so take it easy. It's a tour, not a race. The FDR is pretty easy, even the inclines up to the elevated parts. There's one short, but steep hill when you're up around Broadway heading to the first rest stop, but you'll see/hear people downshifting so put it in the granny gear and glide up. The 2nd half is the harder part because people's muscles tend to tighten up during the rest stop, then they have to climb small inclines and fight headwinds on the Henry Hudson. Again, take it easy and ride your wife's pace.
The 60 and 100 mile routes break off at the Lincoln Tunnel and head up the Palisades I think, then come back over the GWB. It's hilly, but familiar to people that ride that area.