The 12th looks good for me too. Just took a quick look at the "Heritage Ireland" site to get some get some general information. The normal entrance cost is €5.30 but "groups" get a reduced fee of €3.70.
According to the Heritage Ireland people:
"An early Christian site founded by Saint Ciaran in the 6th century on the banks of the River Shannon. The site includes the ruins of a cathedral, eight churches (10th-13th century), two round towers, three high crosses and a large collection of early Christian grave slabs. The original high crosses and grave slabs are on display in the Visitor Centre. There is an audio-visual show as well as a number of exhibitions. Access for people with disabilities to Visitor Centre. Please note that this is a very busy site and visitors may experience a delay during the summer."
Does anyone have any ideas on a meeting time?