You can join RMAS for the AAC up to 28, which may be your best shot, though you won't have confirmation of joining the AAC until your third term at RMAS.
All Regimental Selection Boards are done during inters now (second term). Plenty of 30 year olds kicking round the AAC pilot pipeline at the moment. There is no one under the age of 22. Everyone else is 25 or over; with 25 being considered young and 22 ridiculously young!