It's like the old joke -- Q - "What do you call people who hang out with musicians?" A - "Drummers."

As long as you're not interfering, no one will object. If you have ANY question as to whether the bodhran (or any other instrument, rhythm or otherwise) is appropriate, don't play. Or play so quietly it can't be heard as interfering. If you don't feel you're "good enough" yet, don't stop coming to sessions, just play along VERY quietly. You can't get good if you're not playing with other musicians.

The most important lesson to learn is to learn when NOT to play.

And don't play along with a singer unless the singer wants you to.

Linn