In the family lessons it’s very likely that the members of the group have different levels, while in the group lessons everybody has a similar level.
We do prefer that you have similar skills/levels if you book a private group lesson. If not, the learning process is going to take a bit longer time and you are better off with a family lesson, even if you just are going with a few friends.
For the group lesson we have set a minimum of 2h, while the minimum length of a family lesson is 3h.