Hi,
I'm not too sure about this as I have got 2 dogs who uses the lawn a lot, but at the moment my rabbit have used different areas on the grass for the past 4 weeks and she seems to be fine as long as the grass is set and obvioulsy there are no dog waste left there.
I think it's okay if you remove the dog's waste immediately and leave it for a while til it's 'fresh' and then it should be okay for the rabbit.
Best wishes