Having a baby out later?

Okay, so I’m a FTM so Im definitely unsure of what to do about a few types of situations. I have an 8 month old daughter who I try to put down every night at 7:30-8 (She’s super hard to get to sleep so it’s not exact every night but just somewhere around there). If I’m out or running errands or whatever with her, I try to get home by at least 7 so I can put her down in time for her not so set “bedtime”. We have a family dinner to attend this upcoming weekend at 7 and it’s about 30 mins away from home. Should I let her stay with my mother-in-law (have her come to our house) so she can try to be down by bedtime or just keep her out a little later than normal? I’m sorry if this sounds like a dumb question. I’m honestly still learning and I just want to try to do what’s best for her.