At my gym, we have an old instructor from years ago do reviews sitting out in the waiting area... she watches from afar, listens to parents, and watches coaches on things like attentiveness, supervising kids, spotting appropriately and being hands on, and looking like they are having fun and controlling class. They get (small) pay bumps for doing things well, they get extra training if they aren't doing as well
They can also get these pay bumps if their supervisor notices certain things out on the floor and gives them.
I also go over what I am doing out on the floor with some of the younger staff, or coaches who don't have very fun ideas. I either show them or tell them, and make suggestions about things that might be fun options. I always have a plan b and c!
I think a lot of the lack of enthusiasm comes from just not quite knowing what to do yet! We do not have a big problem with this at my gym, but we also have some really great coaches who have been coaching for years! Having role models and mentors for younger staff has been really essential for us!
My biggest tip is really making sure your staff is working together, and making sure that the coaches are having fun (this does not always mean being crazy energetic though!) I always like to remember "If I am not having fun, my kids probably aren't either!" I am so thankful to work with people who give me fun ideas, help me if I have any kind of accident happen during class, help me brainstorm and set up, and ask if I need help if they notice a tricky kid or situation!
Maybe doing a fun outing, BBQ or a clinic on a certain skill to give ideas and brainstorm?
We have an employee of the month, but it is not particularly motivating- although it is nice to feel appreciated! We also have a coach newsletter with kudos... I have tried to get kudos started on the fridge in our kitchen but it never takes off and they all end up being from me