Tablet PCs are used in various situations in everyday life. Many researchers found that tablets have the potential to enhance young children in learning; however, the optimal of tablet size on finger tracing for young children was not investigated. In this paper, we explored the impact of three different sizes of touch screen tablets: iPad, Samsung Galaxy Tab 7?, and Samsung Galaxy S4 on efficiency and usability for young children ages between 4 and 6 year. Our study focused on the mechanics of tracing alphabets using finger on capacitive-touch tablets, while its outcome has potential implications towards tablet screen size for interfaces to support finger tracing on such devices. The performances were recorded and observed for the analysis of the data with respect to task efficiency and usability. Then, we adopted the Smileyometer based on a 1---5 Likert Scale as an instrument to measure perceived satisfaction. The usability evaluation's results showed no significant difference in speed and accuracy performance. Nevertheless, tracing the alphabet on iPad was easier, more attractive and was able to increase more attention span than others. As well as the result from the Smileyometer, all of the participants preferred and felt more comfortable to use iPad.