I don't want to go on a trip with my girlfriend
Why don't you want to go on a trip with her?
It's because of my family members.
Trips can sometimes be challenging with other family members but it can also be a good bonding experience for all of you. It could make your relationship stronger.
I don't care.
If there are problematical family members, you can work around them. No family is perfect. The positives outnumber the negatives here; you might be pleasantly surprised at the outcome.