That is the best advice if driving straight off homewards after the game and not staying in the town.. Why pay for parking at Brighton station just not logical or cost effective.
If he wants to use a football P & R I would suggest Mithras House as there are numerous buses that go from there to Churchill Sq for his wife's shopping.
Go to Withdean Shoppers Park and Ride you and son will be free with your ticket wifes fare will be £4 you wont park in Brighton town centre for much less and the 27 goes straight to the clocktower. You can get off at the station or stay on to the clocktower and get the 25 bus, again free.