This is a great (and believe me it works!)lesson plan (with step-by-step instruction and tips) for your 1st grade class on fractions and proportion. No it is not too early to begin teaching the concept of fractions and proportion because it involves equal-sharing.
There is even a section on what do do when you encounter problems.

The plan includes amazing visual descriptions of each step along with worksheets for students to complete each step. You will wonder why you hadn't thought about this sooner!