Irie Mon said "Go to the Dollar Store (or where ever) and buy a roll of poop bags. $0.99 will buy lots, and then wonder over with a Timmies or two and have a conversation. Start with " I brought a coffee for you" and then say, "you might not have any of these so I bought some you". Give them the poop bags and their reaction should tell you what kind of neighbour's they will be. The dog shouldn't be running loose, but that's a conversation for another time. "
Frre coffee for a neighbour allowing his dog to do his business in your yard isn't going to get one anywhere. A visit from Animal Control is far more effective in my experience. WE has problems with folks in our neighbourhood letting their cats just wander the community, defecating in people's gardens, and killing the birds that gather at the feeders in peoples' yards. Did our best to try to be nice to the owners, but all we got was halfhearted excuses, or outright hostility. Haven't had a problem since we sent bhylaw to their doors though, in fact a couple even have tethers for their cats now so they can't wander off. Pandering to bad pet owners almost always results in them just walking all over you.