We sought to evaluate the feasibility of conducting a randomized trial to evaluate the efficacy of a preschool/kindergarten curriculum intervention designed to increase 4-year-old children's knowledge of healthy eating, active play and the sustainability consequences of their food and toy choices. Ninety intervention and 65 control parent/child dyads were recruited. We assessed the study feasibility by examining recruitment and participation, completion of data collection, realization of the intervention and early childhood educators' experiences of implementing the study protocol; our findings suggest the intervention was feasible to deliver. In addition, children's sustainability awareness of non-compostable and recyclable items increased. Children in the intervention group significantly reduced their sugary drink consumption and increased their vegetable intake at follow-up compared to control. We conclude with recommendations for revisions to the child interview and parent questionnaire delivery to ensure the roll out of the randomized trial is conducted efficiently and rigorously.