Garden Party is a piece of playful nonsense, and the fun is in how seriously it keeps a straight face. A crowd dances on a "dingbat" in a storm, an alligator winds a kitestring on his tail, and a bassoon player sits down to a catfish dinner. None of it makes ordinary sense, but the speaker isn't bothered. Even the gale doesn't seem to matter: "we do not have to worry."
The second half lists more impossible events: forgotten roses on the moon, chickens floating up on a balloon string, demons knocking acorns down, a pirate ship arriving at last. When all that happens, the speaker says, it will be time for cake and tea. The refrain about "the moral of the story" sounds wise but dissolves into rhyme and sound, so the poem seems to be teasing the idea that stories must teach something.
The mood is cheerful, breezy and a little dreamlike. The speaker seems content to let the world be absurd, and to treat chaos as a good excuse for a party.