The kids at my preschool love drums, maracas, bells, etc…
We made wrist bells for all the kids using pipe cleaners with bells strung on them and then they just hold them and shake them!!!

The number one rule with toddlers whether it be musical group session or training for war, is either give them something to hold or eat. If you had little toy instruments, or possible paper cut outs. That’s an idea Cutting out instrument shapes. That could tie together your whole session – Big colorful musical flash cards. Something overly visual, it may sound stupid, but just imagine your self on a morning time kids show. Characters in kids shows are overly animated to hold a child’s attention, because they lack the ability to touch and talk directly to the child… but you don’t so do! Cause the best way for them to have fun is for you to have more fun, believe me it’s contagious! Good luck no better yet great luck!