We just used this coupon on our last trip. We went up to the bar and the bartender just said to come back to him when we were ready for our next one. We got our first two drinks and tipped him $5. We went up to get another round and waited a long time. He never did come back over to get us our second round of drinks. Maybe just sit at the bar to get the best service would be my recommendation.
We always just get all three drinks at the same time. The bartenders there are always over-worked, and we drink quickly enough that we don't have to juggle three glasses for very long...
In the old days (two years ago) putting a nice tip down with your coupon was always a great play, pretty much guaranteeing good service, but I noticed last Christmas it did not help much, although they were not at all busy when I went to the bar.
The good tip was a good idea but I always found that I ended up paying for the drink at more than full price and or I was tipping a bartender very well for very poor service. Since day one their bartenders have had a dislike for the coupons.