I think it was very nice of you to send a card. That by itself is special recognition.
I have been trying to avoid "advice" but since you asked...since you just set up boundaries and it is still fresh and your family hasn't gotten it through their head yet
AND you anticipate uncomfortable consequences
I would advise you not to phone.
Your mom would probably wonder why the you didn't go to the museum trip.
If you didn't want to be around her drinking...what is the difference between talking to her on the phone when drinking is likely?
Why make yourself uncomfortable? And possibly disturb your peace?
those are just my thoughts...of course, do whatever you want to do.