Margaret Echelbarger et al. write:

Across three studies, we examine the variety selections of 329 children (4–9 years of age) and 81 adults in the food domain. In studies 1 and 2, we find that, like adults, children prefer to diversify their selections given no established preference for one item over another. In study 3, we find that children (4–9 years) diversify their selections more and choose more healthy options when choosing items simultaneously (all on one day) versus sequentially (across several days). Together, our results provide novel insight into the potential for variety to serve as a tool to promote greater well-being in childhood.