Bad feeling about going with friend to a water park?

Well ok in afew days I'm going with my friend to a water park and her 19 year old sister is bringing us along with her baby.It's an hour and ahalf drive there and back and were not spending the night there or anything.My mom even has a bad feeling but I do want to go.Her sister has a history of getting in trouble and doesn't handle resposiblity and won't realy watch us and it's a big park.I'm 14 and my friend is 13 and her sister has a baby and shes bringing him too.Do you think I should still go or should I reconsider?