Marion,
If you went in there thinking "This'll do for them", that would be a bad performance no matter how well you played. They would know.
You, however, go in worrying that you may not be good enough for them. They know this too.
Most people appreciate someone having a go, regardless of the level of their expertise, and those who don't, well, it'll do for them.
Carry on. I can hear it from here. It's good.

Glenn