2 year old spending the night

My two year just recently started staying the night at my mother in laws house, which is perfectly fine with me, she’s amazing. She works weekends, so she has always watched him one day a week. Now though, he has started daycare. I still agreed that it would be best for her to have him a day a week so they get to see each other, but since he started staying the night, he only goes to daycare 3 days a week.

This is starting to bother me cost-wise and it seems to really disrupt his routine, even though he’s not up much later than he would he at home. His daycare is expensive, so it’s hard for me to justify him not going 2 days a week every single week. And it’s not her that brings up him staying the night, he just genuinely wants to stay there and doesn’t want to come home every time we go get him.

What should I do? Do you think it’s better for him to only go 3 days a week and spend those 2 days with grandma? Or should we try harder to make sure he comes up and he only spend the night every once in a while? I’m torn.

And no they don’t have an option where we pay for him to only go 3 days a week.