Your normal day fee of $35 and $40 is similar to rate here. We tend have flat rate for all ages but $35-$40 seem most common based on experience and if meal provided.

I think fee is maybe little low for overnight.

Most charge $100 for overnight if no overlap to normal hours which mean provider able to have overnight child as extra income. Most charge $100+normal daily fee if child going be in daycare during normal hours operating. So if child being dropped off at 3pm that mean space must be allocated to child and parent pay for that space. Then overnight fee. If child gone before daycare open in morning, then that's it. If child still there when daycare open in morning, might be another charge because again, taking a place.

I understand you not go out much as family during week but the $100 overnight is because you will not have option to if want to. It mean evening time is tied to house. It mean no option for grocery shop, bank run, routine task when business day end. It mean no going out supper on special occasion or evening activity for own children. You have be fairly compensated for losing personal time.