I tend to try not to bang on about Mother's and Father's days, as it's a bit odd for me. My parents divorced when I was about 2, I had a great father figure in my young life, I gained step-parents in my teens. I've always found it a bit tacky saying "Thanks" or "I love you" on a set day of the year. So, that's 5 parental figures, and my own stubborn reaction against guilt-trip attempts. Also, I'm now orphaned, but with amazing step-parents. Unpick that mess!
However, I recently saw someone suggest using Mother's Day to thank a carer you may not even realise you have.