How Do You Say No

I went on a little quick trip with my sister and her grandchildren, all five of them. Now the trip we took was only two hours away but it was in a area in our state that have a lot of resorts along with shopping, amusement parks, lots of other different entertainment. I really enjoy the resort we stayed at and the housing facility we had. What I did not enjoy was all of my sister's five grandchildren. The grandchildren was too much for me and found that as I get older and my children our grown and on their own that I myself need a quick vacation without children, especially since I raised my children and did everything with my children, like take them on trips and to amusement parks every year. So now I feel this time is my time but yet my sister talks how much of a great time her and her grandchildren had and she is planning our trip to go next year. She never asked me if I want to go or if I had a good time. Now if she noticed by the end of the trip I was ready to go and one of her grandson had gotten on my last nerve to a point on the final day, I was packed any ready to leave at 7am that morning and check out was not until 10am, the time I actually got us back home and them out of my vehicle. I am not sure how to tell my sister that I really did not find it a fun time for me with her grandchildren, especially when there parents were back home free of children. Why do she make plans with the mother and father to spend time with their children and leave me alone as I plan on taking a trip in the same area but this time with my husband and other adults, no children allowed. I should not have to worry with making sure children are having fun. I need some advice on how to handle this situation, my sister does not drive and I think she just depends on me to take her around with her grandchildren, but again this is not a responsibility of mines, it is hers and the children parents, who by the way take a quick anniversary get away while my sister is stuck with their children. I did not get to have an anniversary when I had my children, me and my husband enjoy our day with our children, if we did get away it was too a movie and back. I do not want to go with my children and her grandchildren. I love them but I just dont enjoy myself and I think my sister knows this but she is willing to ignore my feeling for her grandchildren.