There are a couple of different scenarios going on here. If your constituent is working on a project in their back shed and thinks it might have great application and might be just the sort of project that a government grant might assist with, they are not being paid to lobby. Their speaking with the member of Parliament would not be a registerable lobbying activity.
By the same token, if a person is simply seeking information on a grant program, to know how best to apply for the grant, what sort of material should be provided, and whether they should go to the bank first, that might very well fall into the exemption Mr. Rickford was asking about under paragraph 4(2)(c), requests for information. Simple requests for information are exempted from the lobbying requirements. That's another element.
It can be a complicated question about what is and isn't registerable activity.
By the same token, what you suggested about walking across the hall and speaking to the parliamentary secretary...members of Parliament speaking to one another is not a registerable lobbying activity. So there are complications.