tipping private guides?

We do. Generally, we round up. If the fee is 85 euros, we give 100euros and so on. If we were disappointed with their tour, or they were not on time etc., we tip very modestly. You will be expected to pay in cash. In these places, your guide will be a licensed professional. If part of the days activities include visiting some place where admission is required we also cover that unless it is the sort of place where the guide might have a seasonal pass. If we go to lunch together we sometimes pay but not always - it depends upon the guide.

Ditto