Actually four libertarians (and two and a half larval state libertarians), and it was a restaurant; but the potential for humor is about the same.
Mel and I just had the pleasure of dinner (and Coldstone ice cream afterwards) with Aretae and his wife, and children.
No, there wasn't some long winded intellectual libertarian singularity, or formalist/structuralist matter/antimatter type explosion; though much philosophical geekery did most certainly ensue.
The only problem was that they had an early morning flight back to Texas, so we only had two hours or so to hang out, and barely got past introductions.
Aretae's lovely wife ran out of steam just around the time we (just barely) started talking about compatibilism, utilitarianism, determinism, associationism, the veil of ignorance, the social contract, and the fundamental nature of rights.