Comprehensive article on mismate drug, procedures, reasons for the mismate, and alternatives:
www.vetmed.lsu.edu/eiltslotus/theriogenology-5361/cannine%20pregnancy%20prevention_3.htm
With that posted.. The only thing I want to say that people haven't said yet is.. if your family
afford to provide proper care for your dogs, why on earth are you keeping them? As another [smart] poster mentioned, the price of a low-cost spay/neuter is certainly as much as the cost of internet ($45 for a spay, $30 for a neuter around here). If surfing the web is that important to ya'll... *shrug*
I was Sophie (or hell, even Harry--prolonged sexual tension with zero gratification isn't fun, it's akin to torture) I would certainly want to be spayed, rather than risk all of the crap that happens to unspayed bitches--not to mention the actual heat cycle and how "fun" that must be, I'm sure.
With all of that now said... your excuses for
not neutering are, at best, flimsy.