We live 157 miles from IL's and due to distance we don't see them often. It usually involves us going down to see them, rather than them coming up to us.
We are travelling down the weekend after DS' 1st birthday and I casually text MIL asking did she have anything planned for DS' birthday when we come down and her reply was something along the lines of "No, he will have had a party and a cake at yours won't he"
I am pretty sure although cannot say for definite that she has held small family gatherings for the other 3 grandchildren's (2 live abroad, one lives locally) birthdays if they have happened to be there around the time of their birthday (the weekend before/after).
I dont expect a full flung party or anything etc but I thought as it's his first birthday, she might have a little family gathering with some nibbles etc etc like she has done before in the summer - my reason for the text was I was going to say we could buy the food etc so she didnt have to outlay any cost which she normally does if every she lays on a buffet for a gathering.
She's only seen DS when he was 2 weeks, 4 months, and 6 months (maybe another time too) which is when we have gone to visit them so I thought she'd maybe want to do something to mark his birthday.