Forget the holes, why ruin a perfectly good plug.
There's stuff called 'Sticky Putty' or something which is a moldable adhesive you can find in an art supply place or maybe 'Michael's' craft stores if they're any by you - just roll up a long bead, apply it to the plug and stick it to the driftwood.
Look, Ma, no holes - but shoot quick 'cause it won't stick forever.
Ain't product shoots a blast

- hope you two are still speaking - who's the art director on the job?