It's completely okay to tell them you're going only because you want them to know.

It's also completely okay not to tell them all the reasons why you're there - because you don't want them to know.

Say all that you want to say.

And keep all that you want to keep to yourself.

There's no harm in that.

If your parents can't understand that then you may face a real struggle there... Really you decide whether they respect your wishes or not. They can't force words out of your mouth that you don't form.

It's fine to wish for their acceptance but it's also fine for your to wish for their acceptance that you won't be telling everything.