Ok, I’m sorry if I misinterpreted what you meant- though I’m not sure what you mean by the stepchildren should be a bit more thoughtful, if it isn’t that you think they should have got her a Mother’s Day card/gift, even though they did not want to? I’m not sure what else you can be suggesting?
Either it is ok that OP’s step children did not wish to get her a Mother’s Day card as they don’t view her that way, or it isn’t- and if that is the case, they should have done so regardless of how they felt. You said it would “be nice if they were thoughtful” which to me suggested, in this context, that you think they ought to have got her a card.
if you think they should have got the card, regardless of how they feel- then that is suggesting that they should express sentiments towards OP that they do not hold, so that she feels better. Which I think is wrong.
If you are saying it would be nice if they did appreciate what OP does- I agree, they should. But it is completely appropriate that they do so in other ways that are unrelated to Mother’s Day.
OP said her DH has the stepchildren every other weekend and one day during the week (so 6 days out of every 28) and a bit more during the holidays (but does not say if that is 50%, or more/less than 50%).
With regards the holiday, another poster quoted that from one of the OP’s previous threads, but I have no idea if it is accurate which is why I said “I read”, rather than “OP said”. In any case, we don’t know if OP told her step-children she had paid for them to go on holiday, whilst their father contributed nothing- I imagine they just thought they went on holiday with his dad and his wife/her children. Which they may/should have been generally grateful for, rather than specifically grateful to their step-mother (though I have teens and they have yet to specifically express gratefulness for family holidays- they are happy we go and generally show appreciation for things done for them, but I would not expect a specific “thank you so much for a holiday”, if I’m honest). But if they were made aware that they only got to go on holiday because step-mum paid, I would question why OP and her DH would inform them of the financial ins and outs of holiday payments? What would the purpose be? Not one in the best interests of the children, I would have thought.