I had a card from my DSC "to my fabulous stepmum", which was lovely, and they woke me up by jumping on us to give it to me. DH brought me coffee and toast in bed.
They went back to their DM's late morning and her new bf had taken them shopping to get some gifts. All very uncontroversial rounds ours thankfully.
I've sorted gifts with/from them for father's day and DH's birthday since we moved in together as their DM hasn't ever done anything for any of it.
This is her first relationship so in the past we/I've taken them shopping for small gifts for occasions - e.g. we got her a pair of earrings for xmas when I was with them buying DH's gift from them.
It's a lot about the joy of giving for the DC. They often choose mad but incredibly sweet gifts and love an occasion.
DH and I give each other a lot of cards and small gifts - sweets for him and second hand books for me most of the time, also socks, jam, bits for the house - and they pick up on that and want to be part of it.
DSD is forever wrapping stuff in tissues, DSS makes a lot of things out of Lego or he'll gift wrap the can opener and hand it over as a present.
Mother's Day, Father's Day etc can be commercial and stressful, or nice excuses to make a bit of extra effort to show your appreciation and my card and toast reminded me that they value what I am to them and do for them - or they just wanted a piece of the giving stuff that was everywhere, and that works for me too.
I don't expect gratitude from them but that DH appreciates how much I do for his children and to support him means a lot to me. On mother's day and all the other days.