As an American learner, I was surprised to find Mothers Day to be celebrated on the second Sunday in February in Norway as well as many other European countries; it's an interesting difference.
So a little early for American standards but pretty late for Norwegian standards, I'd like to say: Gratulerer Med Morsdagen! (Hope that's correct)
Wasn't it said somewhere else that we had to use "er glad i" instead of "elsker" for family, friends and not romantic relationships? I've seen this a few times now and it's a bit confusing, and I'm starting to think the difference between the two aren't really that big, are they?