Im no expert but would say at 8 and 9 months, that they could be making pups
its great that you are wanting to get them both tested etc before considering pups, as far as stoping a pregancy, I would suggest that you would have to ship the bitch off to a friend or familys house whilst she is in season, as it only takes a few moments for them to have done the deed, its also not fair from a stress point of both dogs as the male will be driven wild normaly by the smell and the bitch will be trying to lure him or get away i imagine too
im no expert, but hope you find the right solution quickly
out of interest what made you decide to become a breeder ?
Phil