I had an episiotomy with Jenna due to the forceps labour, and I was worried about tearing with Hamish.
I had absolutely no problems, and he was pushed out quite quickly with a normal sized head, and I didn't tear at all. Just a couple of grazes.

Afterwards the midwife was surprised that I had had an episiotomy at all, she was watching the whole pushing stage and never mentioned that I didn't have enough "slack".

Try not to be too worried about anything happening. Leave it up to nature, but be prepared and do your perinium workouts now