Ron said they did Mother's Day for his wife on Saturday, and then Shelly and the kids were with her mom on Sunday. He said they aren't necessarily tied to specific dates for celebrating holidays, which I don't think is unusual for the kinds of jobs they've always had (Ron working overseas when he was deployed for the military and then again when he was painting ships, and Shelly working 12 hour shifts as a pipefitter). And though I don't get the creeper vibe from Ron, he does have a big personality (to put it mildly), and I could see where celebrating Mother's Day for Shelly's mom when he's out of town might be best for everyone.