I said the exact same thing to the 4 bosses I e had over 8 years. ‘Just to let you know, I have a stutter and sometimes find it extremely hard to get my words and join in or strike up conversations out so please bare with me’ Every one of them were extremely supportive and understanding. Don’t worry about telling them, I did but as soon as I did I felt a weight lift off my shoulders, it’ll be fine don’t worry!