Mary,
She is so adorable. Congratulations for such good works (both baby and pictures).
I would probably use pastel or watercolor for a more liberated expression, add more color on the background, maybe color coordinated series on each pictures (Rose, pink, orange, peach...). For the size I would do less than 10 inches square (10" X 10" or 8" X 8"), and frame them separated, but hang them together.
If you think this is not enough, then do a larger one or an oil later; you will need much more energy to finish them all.
Genway Gao
