By my calculations, if the club do not inform members of price changes today, then they cannot change them until December. This is because they won't be able to give the 90 days notice required before November's payment.
The gratis shirt is the catch. The club have a surplus of kiddies-sized shirts given no-one can afford to pay the increased membership price for kids. You'll be seeing a lot of small dogs wearing City shirts in the not too distant future.