I need some advice mommies!

I'm going to start from the beginning. I got pregnant and my so at the time and I broke up when I was 3 months along. We never got back together and he never really cared that we didn't. Rarely checked up on baby and I. His parents and I stayed close. Well he passed away 5 months ago. My daughter is now 18 months old. She goes to her grandparents house (his parents) every Sunday for the day. She has been since about a year old. They are going out of town this weekend and asked if they could take her to meet some family. I don't want to say no because I do want them to meet her. But she's never stayed overnight with them. She's only stayed over night with my mom. I'm worried if I let her go with them shell be scared and cry the entire time when I dont go to pick her up after a day. They'll be gone 3. I'm not sure how I'm going to handle it either :( any input is welcome!