Maxillary constriction and deep bite.

Hi Everyone! Initial Ortho consult for twin 13yrs old brothers. Both presented with similar condition - Maxillary constriction and deep bite, mild crowding. Mother is wondering if we can do functional appliance to expand both arches and avoid brackets, because they might not be compliant with oral hygiene. She was advised that they will need phase two to obtain proper alignment. Is it right to do expansion upper and lower arch at 13 yrs before straight wire? Or would it be enough to choose straight wire treatment (using DLX acrh wires)? Thank you!