When teaching children about that age I try and change up the activities often. Children that young have very short attention spans and shouldn't be tasked with focusing on one thing for too long.
I generally switch activities up every 5-10 minutes. You have the right idea with the songs. Try to come up with some themes (such as teaching animals, numbers, colors, etc) and teach from there. Themes help students focus on certain areas.
Also, try downloading some flashcards and playing some simple flashcard games. Check out
Dave's ESL Cafe for some great ideas for flashcard games and tips on teaching young learners. You can get some flashcards and other material from clicking on the links in my signature.
Good luck with your new little friends!