A convertible highchair is described that includes a bucket seat with a contoured backrest and an adjustable harness to securely and comfortably hold an infant in place while eating or performing various activities. The bucket seat, acting as an infant seat, is also removable to accommodate infants of different sizes and ages. For instance, the bucket seat can be removed to transition the highchair from use as a baby feeding chair to use as a toddler feeding chair, where a toddler seat is height adjustable. The highchair also features a removable tray that is adjustable in distance from the infant to allow for easy access to food and drinks. The tray can also be equipped with a spill-resistant lip to prevent food and drinks from spilling onto the infant's lap or the floor. The highchair also includes a sturdy base with legs that ensure stability on various surfaces.

A child booster seat assembly is provided and includes a base seat and an upper seat. A first seating area is formed on the base seat. A second seating area is formed on the upper seat. The upper seat is detachably installed on the base seat. At least one first guiding structure is formed on the upper seat, and the at least one first guiding structure protrudes from a rear bottom portion of the upper seat and extending along an installation direction of the upper seat relative to the base seat for guiding the upper seat to be aligned with the base seat when the upper seat is installed on the base seat.