I've always tipped in US Dollars...They seem to be accepted everywhere...no one's ever seemed to show any upset when receiving them...
On shore excursions, I think the standard is about $5 a couple on a half-day tour and $10 on a full day tour...and I'll also give a couple of dollars to the bus driver as well...
And it varies...
I've givent better tips to some exceptional tourguides...
...and then there's the tour guide we had in Villefranche...
In Eze, she promised us a really good view of the sea with the ship and everything...then told us, no, it was closed...but, when we got back to the bus, people in the next bus told us THEIR tour guide found them a great spot where they got great pictures and everything...
In Monte Carlo, the guide on the OTHER bus took the entire group[ through the Palace (even though admission wasn't included in the tour, they all anted up and she took them)...Our guide left us off in Monaco and just told us to meet back at the entrance to the Oceanographic Museum at a particular time...When we got there at ten minutes 'til, a group of us was forming...We waited until about ten after and started panicking because the guide wasn't there...I FINALLY convinced the others to follow me because I knew the way back to the bus...When we got there, the guide and some of the tour were already on the bus...When I asked, she explained WITH NO APOLOGY that ir was hot, so she went back early...
Yeah...I STIFFED HER...NO TIP!!!