just by first name or with the word Aunty / Uncle in front?
I've always been Tante (German for aunty) Ria to my youngest niece and nephew (7 and 10 respectively) and I love it.
A few times now though this particular niece (A) has just called me by my first name. Now all the other nephews and nieces do as well (aged 15 - 29) and I really don't have any objections - I leave it up to the parents to decide how the children should refer to various relatives - but I just find it quite sad that A has started dropping the Tante bit
they are all just growing up too fast