^^ Good stuff from the other posters. I wouldn't text or even email W to wish her a HBD. She's demanding and dictating you how to parent the kids when she just upped them and moved 4 hours away. Perhaps have the kiddos cut out a homemade HBD card for W from them....just throwing out an idea here. Make it about the kids and their Mom.
One question...do the kids have Spring break vacation up in Canada? Or some scheduled holidays/days off from school that is happening in the next few days/weeks?