I'm in your situation this year OP... new baby boy plus a 12 year old DSD.
My family have of course spoiled my DSD over the years with nice Christmas presents, and I'm sure they'll do the same again. We have her 50% of the time, and she is completely part of the furniture, likely will be there at my parents for Christmas dinner, comes on extended family holidays, etc.
However - she gets bloody TONS at Christmas as it is - as she gets a 'big' present from her mum and stepdad, and then another 'big' present from her dad and I, plus all the usual grandparent gifts, and gifts from her wider biological family, PLUS any nice gifts from my wider family & her stepdad's wider family. Her friends (who's parents are still together) have commented on how lucky she is and how unfair this is, as when most kids get, for example, a computer as their main Christmas present from mum and dad... she might get a computer at one house (from her mum and stepdad) and a PlayStation at the other (from her dad and I).
I know without a shadow of a doubt that my parents are not going to even begin to try to equate the gifts they buy for my baby with the gift (likely singular, albeit generous,) they buy for DSD. And that's more than ok - DSD has her own grandparents to spoil her, plus double gifts from her parents / stepparents because her parents are not together. My own DS, as he grows up, will actually more than likely notice he doesn't get as much overall at Christmas as his step-sister, as while we will treat both kids the same under our roof, my DS will only have one house and no step-parents and additional wider families to contribute to gift giving!!
I don't see how you could demand that gifts from your wider family be equal - to me it would come across as rude if I received a message along those lines about gifts I was buying, and it's really not necessary at all from your stepchild's perspective. (Nor is it particularly appropriate, in my view.) As long as in your own house you're treating them equally, I don't think you need to get into trying to go beyond that.