A chosen name deserves the same ordinary ease as a familiar one.

Using a name someone has chosen is not a favour, and treating it as one is most of what makes it awkward. What is being asked for is not enthusiasm but ordinariness: saying it the way you say any other name, with no pause, no look, and no small speech about how well you are doing. Every extra bit of ceremony marks the person as an exception. Ease is the whole request.

If you get it wrong, correct yourself in three words and carry on. Practise the name on your own if you need to, so the practice does not happen in front of them.