Support device for a child accessory, the support device comprising: - a plurality of support legs, wherein said plurality of support legs comprises at least one first pair of legs (2a, 2b); - at least one main crosspiece joining, and fixed to, respective upper ends of the first pair of legs (2a, 2b) and extending along a main longitudinal direction between such upper ends, the main crosspiece having at least one first intermediate portion extending transversely with respect to the main longitudinal direction and to a line ideally joining the upper ends of the first pair of legs (2a, 2b); - at least one third leg, movably mounted with respect to the first pair of legs (2a, 2b); - at least one first auxiliary crosspiece fixed to an upper end of the third leg, said first auxiliary crosspiece being configured for being rotatably connected to the main crosspiece at the first intermediate portion; and - a first coupling pin, configured for determining and keeping at least temporarily a hinge connection between the main crosspiece and the first auxiliary crosspiece; the support device being characterized in that the main crosspiece comprises a central portion and a locking key for a child accessory, said locking key being configured for assuming at least one first use position wherein it is configured for constraining the child accessory to at least the main crosspiece and a second use position wherein it is configured for releasing the child accessory from the main crosspiece, the device being configured for allowing a switching between the first use position and the second use position of the locking key by means of a rotation movement and/or an axial movement and/or a combined roto-translational movement between the locking key and the main crosspiece. - a plurality of support legs, wherein said plurality of support legs comprises at least one first pair of legs (2a, 2b); - at least one main crosspiece joining, and fixed to, respective upper ends of the first pair of legs (2a, 2b) and extending along a main longitudinal direction between such upper ends, the main crosspiece having at least one first intermediate portion extending transversely with respect to the main longitudinal direction and to a line ideally joining the upper ends of the first pair of legs (2a, 2b); - at least one third leg, movably mounted with respect to the first pair of legs (2a, 2b); - at least one first auxiliary crosspiece fixed to an upper end of the third leg, said first auxiliary crosspiece being configured for being rotatably connected to the main crosspiece at the first intermediate portion; and - a first coupling pin, configured for determining and keeping at least temporarily a hinge connection between the main crosspiece and the first auxiliary crosspiece; the support device being characterized in that the main crosspiece comprises a central portion and a locking key for a child accessory, said locking key being configured for assuming at least one first use position wherein it is configured for constraining the child accessory to at least the main crosspiece and a second use position wherein it is configured for releasing the child accessory from the main crosspiece, the device being configured for allowing a switching between the first use position and the second use position of the locking key by means of a rotation movement and/or an axial movement and/or a combined roto-translational movement between the locking key and the main crosspiece. the support device being characterized in that the main crosspiece comprises a central portion and a locking key for a child accessory, said locking key being configured for assuming at least one first use position wherein it is configured for constraining the child accessory to at least the main crosspiece and a second use position wherein it is configured for releasing the child accessory from the main crosspiece, the device being configured for allowing a switching between the first use position and the second use position of the locking key by means of a rotation movement and/or an axial movement and/or a combined roto-translational movement between the locking key and the main crosspiece.