If I am with a Deaf friend and cannot simcom, what is the most polite thing to do?

I am learning ASL. A friend of mine is coming over with her grandkids to ride horses with me. Her grandkids are all hearing, and my friend is Deaf. I know there will be times when I need to be paying attention to all the youngsters running around, and will not be able to sign adequately what I want to convey to the kids. I don't think they all sign very well, also. What is the most polite thing to do? Should I ask my friend if it's ok if I use my voice and then try to translate later, or is it ok to give the kids instructions while she watches, any suggestions??