My friend's children, and DD's friends call me Pavlov. Sometimes her friends call me LittlePavlovsMummy and i tell them they can call me Pavlov if they want to, sometimes they do, sometimes they don't, I don't mind either way. I do not want to be MrsPavlov to them, it makes me feel old.
DD and DS call very close friends Aunty and Uncle, those she refers to as that are those who are in fact aunt/uncle like in their relationship, rather than everyone we are friends with, everyone else they call by their first name. Some friends who are not so close want the children to call them aunty (for some reason, it is more the females that want this than the males wanting to be known as uncle), and if that floats their boat then I dont mind the children calling them that, but when we talk about those adults we just refer to them as their first name.
But, YANBU to not want it if you dont like it. But, in that case you have to make it very clear that they must call you by our surname. But it is very stuffy.