I use a tow bar attachment for my mountain bike and my daughter's full 20" wheeled bike. I know i'm not in the same exact situation as the OP but here's my solution. since i can't tow w/ my fixie or roadie, and i get way too tired pulling her and her bike w/ my street tire equipped MTB (the 26" wheels ain't doin it for me), i'm planning on getting a mixte frame. it is a step through frame that seems sturdier than the curved/bent double down tubes of normal women's bikes..... maybe you could do the same? they all come w/ eyelets, and if you get an older frame meant for 27" wheels....i'm going to use 700c w/ long reach brakes and tow her with that...i can probably fit up to 32mm wide tires... or is there still the stigma of men not being "a real man" when he rides a step through frame? BTW, my dad's 73 and he rides a newer schwinn voyageur "ladies" frame.....