As xcgb said, make sure you have a back up, even if it’s just the vicar stepping in to help out.
Five years ago i was determined to be a pallbearer at my brothers funeral, thankfully the funeral director had an extra person on hand on the day as when i arrived at the church i needed my mrs to help me in the church, let alone be able to help carry a coffin.
My brothers best mate spoke on the day and he smiled, laughed and cried as he relived stories, none of which mattered as the whole congregation was doing the same along with him, if what you say is from the heart then there will be no problems even if you have to pause to compose yourself.
A couple of fresh hankies will be essential, my thoughts are with you for the day.