Whirly beat me to it!
I was just thinking the same things as she was.
When you get your PPL, you might be a qualified pilot, but you WILL make plenty of mistakes afterwards. Someone once told me, that on every flight you take you will make at least one mistake, and they were right.
Some of these as very minor, and some are more significant. As your experience increases, and you've made the mistakes before, you'll learn to quickly deal with them, but in the begining, mistakes can be more stressfull.
Best to make them when you are either alone, or with friends, and not with strangers, and under pressure.
I suspect you will also be put under pressure to fly in weather conditions that you might not be happy with, given your level of experience, expecially if there are more experienced pilots flying that day.
For what it's worth, I believe such flights would also be illegal in Ireland. As I understand it, we don't even have the cost sharing rule here. PPL must pay full cost.
dp