Great thread.
Living in Perth this has been a constant challenge since my son was born (2001 as we were starting to slide). Thankfully his Mum has got on board so that we have a united anti-Eagles and Dockers front. For me the keys have been:
Teaching and constant singing of the song from day 1
Going to games and family days/functions when they are in Perth
Phone calls from Nanna and Pop to talk Carlton - this is a good one.
At least one trip to Melbourne each year for a game (with my mates and their Carlton kids - happens to be this week

)
Bribery - jumper, doona, flag, football, posters etc
The hardest has been this year since Auskick has started and almost all the other kids are running around in Eagles jumpers with "3" on the back. Anyway, Tom still goes with his Navy Blues jumper and wears it with pride.
(He also has a passionate hate of Collingwood, Essendon* and Port Adelaide so even if one day he defects he will never follow any of those)
Go Blues
I think you have things well under control.... defection won't be a problem I' sure.