In Spanish we don't necessarily have to use the personal pronouns all the time. Sometimes it makes the sentences too long. I would suggest to eliminate a few personal pronouns...even if the audience is kids.
Deseamos que estén todos bien. Estamos de regreso en Canadá, pero a pesar de que estamos lejos no los hemos olvidado y los extrañamos mucho. Queremos desearles a ustedes y a sus familias una muy feliz Navidad y un feliz Año Nuevo. Les tenemos un pequeño presente y esperamos que les guste.
an I also think "presente" is ok although maybe it's better to use "regalo" in this case. I am positive kids understand "regalo" better than "presente".
