This may be too late for your observation this year but you might use it again next year.
I use the story about the old lady who swallowed a fly.
I have a puppet with all of the animals she swallowed. We read the poem previous to the lesson where I use the puppet.
After going through all of the animals (with them still inside the old lady), I begin to remove them one at a time and we make a list of all their names. I discuss that all of these animals are things. This leads to the definition of nouns.
Then I teach them the noun jingle (from the Shurley method of teaching language). It goes like this: This little noun, floating around, names a person, place, or thing. With a nick,nack paddy-wack. These are English rules. Isn't language fun and cool? (sing to the tune of "This Old Man")