I think that was a great gesture! I'm sure it made their day. One of these days I will figure out what the proper protocol is...
I kind of like how they do it on cruise ships - they set a baseline tip that's automatically paid, and you can choose to adjust it up or down at the end of your cruise. I think it goes to your room steward, your waiter, and one or two others.
We ended up leaving with the understanding that basically anyone in the service industry was up for a tip. If they helped you in some way by making your experience better, then you could choose to tip them. Some on the pushy side got nothing from me. Those open roof double-decker tour busses in NY - most of the people running them got nothing - they would basically wave a tip jar in your face. We did get one guide who was so helpful - I gave him about 25%. He was so grateful, so I gave him another couple of singles, just because.
If you have to tip, then, yes, you're right. Cruise ships do it really well. But then payment systems on those are linked to your card which is a bit difficult to do across different businesses in a country!