Here's an easy song you will no doubt find many uses for. It's short, it's simple, it's unison, and it's easy for your young students to memorize. It also has a couple of little moves that are easy enough to do or not, as you prefer. Plus, the snazzy light swing accompaniment on the recording will help keep singers in the groove whether they're moving or just singing.
For a broader use of the tune, substitute other lyrics as needed. For example, "Welcome to our class." Your visitors will definitely feel welcome! (from Music K-8, Vol. 20, No. 1)