At what age did you leave your LO overnight with family?

My 3rd baby is currently 15 months. She's been on one midday nap since about 10 months old (due to daycare). She woke overnight 1-2x up until she turned 1. Then she'd go the full 11-12 hours at night w/o waking except the last 2-3 weeks she gets up once a night, probably due to teething. Maybe this will stop once the molars are all in. All this to say, she’s fairly low maintenance, imo.

With my oldest two (14 & 12) | never left them overnight with my parents until they were around 2/3 years old. I honestly feel like it's sort of inconsiderate for mom & dad to leave a baby under 1 overnight with family, especially if they wake overnight, BUT I understand that's my personal feelings. However, now that my baby is over 1, I'd like to resume taking a trip or two a year with my SO without her.

The thing is, my parents are now divorced and my dad works 6 days a week from 4AM-4PM. So he is 100% not an option. My mom works normal hours, Mon thru Fri 7am-4pm so she would be able to drop off/pick up my LO from daycare if I was gone 1-2 weekdays/nights and weekends shouldn’t affect much.

My SO has a trip planned late August, so she will be 18 months at that point and bc it's a 9 hour drive, we just cannot bring her with. It's from one midwest state to another, no flights available - it's literally drivable only. Anyhow, I brought this up to my mom and she's saying she really doesn't think she wants to keep her overnight for more than a night or maybe two and not during the week.

With this being the case, I feel like I’ll have to skip the trip unfortunately bc i can't justify driving 9 hours to stay 1-2 nights. But it got me thinking, when is it acceptable to have her stay overnight for more than 1-2 weekend nights? My in laws live a few hours away, but I know my MIL would be one hundred percent on board to watch my LO for as many days as needed. I just feel guilty asking her to take time off to come stay at our place for a long weekend (their home is way out of the way of the trip, so would not be ideal to take our child there). If you were in my spot, would you just ask your in laws? Or wait till next year and hope the in-town grandparent will be willing?