When composing in first grade with use a grid with 16 "beats". Each box equals one beat. Instead of using notation or words, we created symbols for the instruments in our group and drew one for ta (quarter note) or two for titi (two eighth notes).
After composing individual rhythm songs in groups, students performed them together. What glorious sounds! What amazing music readers!
I also love to use a Rhythm Stick Reading Station and an Instrument Reading Station with students. This allows them to read icons for instruments and rests and play together. This is great for workstations, small groups or large groups (my favorite!) Check them out: