Activity for Alexa

I am trying to figure out how to put this on my invitation/website. I don't care about dress length, just that it's not crazy or casual. I was think semi-formal, but I am honestly not really sure what any of these types look like and google doesn't...

I am honoring my fiancé's grandmas and my aunt by having them walk down the aisle. I have an usher for my aunt and his other grandma will possibly walk alone(still trying to work this out), however, my fiancé's other grandma is married and I want her...