Historically, learning for young students has occurred in formal, in-person classroom environments. But in just a matter of weeks, children were mandated to transition to a completely new mode of learning, facing new learning challenges with heightened anxieties. To this end, we aim to better understand how our learning experience design (LXD) efforts support or hinder children's engagement while participating in an online, video-based math course. This study operationalized LXD through the integration of e-learning instructional design (ID) as a lever for promoting students' situational interest (SI), emphasis on human centered design to support students' user experience (UX), and the combination of SI and UX to foster student engagement in an online environment. Results provide practical implications for how we can intentionally iterate our designs to sustain children's online engagement as we prepare for future instances of traditional, online and even hybrid models of instruction. [This paper was published in: "ICLS 2021 Proceedings," ISLS, 2021, pp. 521-524.]