I know that behind the scenes jws have many ways to tell themselves it is okay to celebrate despite WTS official positions on them...shows that jws are only concerned about getting "caught" by humans not their god.
ijwfq 59 (frequently asked questions) direct link to WOL: don't click if it will trigger you: https://wol.jw.org/en/wol/d/r1/lp-e/502019300#h=43:0-47:358
Or reasoning from the scriptures book:
What is the origin of the practice of setting aside a day to honor mothers?
The Encyclopædia Britannica says: “A festival derived from the custom of mother worship in ancient Greece. Formal mother worship, with ceremonies to Cybele, or Rhea, the Great Mother of the Gods, were performed on the Ides of March throughout Asia Minor.”—(1959), Vol. 15, p. 849.
This article is fairly recent and lists holidays that are also non-religious of the ones not to celebrate (just reporting, not supporting)