Playing on fingertips is essential for proper piano playing. Playing the piano with the 3rd finger supported by the thumb helps reinforce this concept for children from the beginning. Both the Donut and Twinkle Twinkle Songs should be played with this hand position. Think of your 3rd finger like a woodpecker's beak tapping the piano keys
To learn about short sounds at the piano I created this version of Popcorn Popping.
"I looked at my piano and what did I see (make donut shape w/ fingers 1 &3 (see p. 15 of Piano Adventures Writing Book) and put both hands to your eyes to make glasses
Popcorn popping on the piano keys (Play Short sounds on a key on the piano w/ your 3rd finger supported by thumb - a 3-1 donut)
Spring has brought me such a big surprise
Popcorn popping right before my eyes...etc." (Play Short sounds)
Finish the song as usual.