
Hi Hayley,
Congratulations on your new house - how exciting!
Yes, disinfectants will eventually kill grass. The best thing you can do is have a watering can at the ready and immediately soak the area. The good news is that if you don't do it, the grass will die but eventually will come back stronger and greener than it was orginally! :-) There are also products you can buy that are supposed to help, they are added to your dog's food. I don't know anyone that has used them, so I don't know if they really do make a difference.
By the way - does Harvey lift his leg to wee? If he does it's not your grass that will suffer, it's the plants and shrubs. Not all of them, some of them seem to be impervous. Only the expensive new ones, or your favourite ones will sucuumb. If he decides to lift his leg against an unglazed terracotta pot on your patio - well, it will reek for some time afterwards. :-(
I have a bitch and a dog and still manage to have a pretty garden, so all is not lost. Drought, moss and heavy clay soil have done more damage to my lawn than my dogs by far.