A seat assembly comprises a booster seat with a lower support surface and an upper seating surface. A back support extends upwardly at the rear of the upper seating surface and side supports extend from the back support around the lateral edges of the seating surface to merge with the upper seating surface. A supplementary base has a peripheral edge to engage the periphery of the lower surface to provide increased lift. The base has an aperture dimensioned to receive the back support and side supports so that the base may be inverted and nested on the upper seating surface.

An attachment for an activity table according to the present disclosure includes a clip having a first attachment mechanism on a first end, a second attachment mechanism on a second end opposite the first end, and at least one hole shaped to receive a fastener; and an accessory having an interactive element and at least one aperture configured to receive the fastener. The first attachment mechanism is configured to insert into a corresponding slot of the activity table, and the second attachment mechanism is configured to snap fit to the activity table.

A system, method and/or kit for assembling multiple different children's accessories using shared or modular components or parts to assembly multiple different accessory modalities or configurations. In example embodiments, the multiple different accessory modalities or configurations may include one or more of a gym or play mat, a play gym, an activity jumper, an activity center, a play table, and/or a playhouse.

The present disclosure discloses a wheel assembly structure and a child activity center. The wheel assembly structure includes a connection base and a wheel assembly that is deployable. The wheel assembly is pivotally connected to the connection base. The wheel assembly has a deployment state and a storage state. An adjustment mechanism is provided between the connection base and the wheel assembly. The adjustment mechanism is configured to switch the wheel assembly into the storage state from the deployment state. When the wheel assembly is in the deployment state, the wheel assembly is deployed to a first position to move the connection base. When the wheel assembly is in the storage state, the wheel assembly is stored to a second position to stably place the connection base. The wheel assembly structure has a simple overall structure, which facilitates production and lowers production costs.