A few personal opinions, based on the sessions I've been to in Co.Clare :
1 - no session ever needs 3 guitars playing at the same time. Assuming the 3 guitarists all knew the tunes being played, [ and that is a requirement ] would they be content to take it in turns to play, rather than all 3 playing at once ? And the session in question may already have a regular guitar player, in which case all 3 are superfluous, unless invited.
2 - the sessions in Co. Clare I've been to are of a very high musical standard. They are no place for a "novice" bouzouki player. He / she would be best advised to listen.
3 - They're not short of bodhran players in Co. Clare. Again, one is enough, [ and some would say too many ].
4 - a possible solution, based on something which happened on the West coast of Scotland at a session I was in 4 weeks ago. A French guy comes up to us and says, could he and his friends play some music at some point in the evening ? We thought maybe one or two fiddlers or something might want to come and join us, but no, there were 7 of them, from Lyon, I believe. I don't think they knew any of the Scottish and Irish tunes which were being played, and in actual fact, the physical constraints of space precluded them from joining us, but they were invited to play some of their music, and did so, a few sets of tunes lasting maybe 15 minutes in all, twice in the course of the evening. The regular musicians had a break, and enjoyed their playing, then got back to the usual session. Everybody happy.