Gaon,
I am afraid you may be confusing two different issues. The first, which is what the S”A you cite is discussing, is giving gifts to a Nochri around Yom Eidum.
A totally different issue is participating in an act of A”Z when that act is part of the way of the worship. With the issue at hand here, the problem is that giving the sweets is part of the act of the A”Z and so the section of the S”A you cite is not relevant. Even if there are many nochrim who no longer understand why they do the specific act of A”Z that they do, it is still prohibited.
Imagine, if you will, that people still performed Peor to Baal but most of them did it today because it was a fun thing to do and not because they believed Baal was a deity. That is the issue – not stam gifting within three days of Yom Eidam.