Hi Andy.. ..
The Tassia is at the end of the Laganas main road and a fair walk into the resort and further to the beaches but, it's a nice place to stay and Costas and his familly who run the Tassia are really nice people.
You can catch a bus into town from a stop just along the road and Costas will sort you out with the times etc or call taxis whenever you need one.
Laganas in early May can be hit or miss with the weather but as your going on the 18th you should have great weather although it can be on the cooler side at night time.
The resort is well up and running by mid May and i've been 10th - 24th May and 5th - 20th june over the last few years and the first week of the May holiday was fairly quiet in the town but it picked up and got busy in the second week. The june holiday was full on in Laganas so you seem to have picked the dates well.
Anything you need to know about who's going the same time as you and the clubs and reps look over the
http://www.laganas.me.uk site as it seems to be the best resource for Laganas and the night life.
paul..