My step mum has said that I need to start sending birthday cards to my step niece/nephews (her grand-children) now that I'm expecting my 1st child! I have hardly any contact with her family and have seen the family about 6 times in 7-8 years!! I always send Xmas cards and cards for special birthday. I feel it'd be wrong just because I have child! Also, I don't get birthday/xmas cards from them! (That sounds immature but hey ho!) Am I being stubborn/ureasonable?
Do whatever you feel comfortable doing!
For the record, I think that what you are doing now is great - you're acknowledging your extended family on special occasions, which I personally feel is alot more heartfelt than going through the motions of checking your calendar and sending something out of (stepmum imposed) duty!
Hope this helps!