Am I being over dramatic

So my sister in law has 2 older kids, 10 & 6. And she wants me and my husband and daughter whose 5 months old to go to a water park with her this Friday the 1st. We have a vacation we've been planning for months coming up on Tuesday the 5th. And i don't want my daughter to get sick or anything before our vacation. Am I crazy to tell my sister in law that we don't want to take my daughter to the water park in case she gets sick? I know there's a ton of kids and germs at water parks and younger babies shouldn't even really go. Or am I being over dramatic?