as long as your friends look 18, and don't act the clown they should get in no probs, its unlikly they will be asked for i.d.
go and enjoy yourselves your only young once.
p.s ignore the misery guts that will proberly reply by saying,you shouldn't be drinking its against the law.
your on holiday enjoy

Drinking age in Ibiza is 16. Unless they have changed the law recently.

The drinking culture is very different, its not unusal to see 14 year olds drinking wine and beer in cafes. You are very unlikely to be IDed unless you look really young, and I think legally you are probably fine anyway.

here's a thread i found with the correct information

http://www.holidaytruths.co.uk/viewtopic.php?t=96300

on the subject of clubs and doorstaff i imagine that with recent closures and fines for allowing illegal things to go on inside clubs that the security staff would be really on their toes and on the lookout for anything untoward.

http://www.mouse-ibiza.org