Do go to Meis - it was a fun trip and very relaxing after all the walking!
For the trip up into the mountains to Arykanda and the walk - it is definitely a lot cooler up there so take a long sleeved top or wrap. It rained when we were there and I actually felt a little bit cold for some of the walk in the forest.
The Cavdir to Uzumlu walk was through some very brambly, scratchy plant life so wear longer trousers or socks that can be pulled up. The trout lunch at the cafe was delicious.
Lamanagzi beach is really pebbly and rocky so some neoprene socks/aqua shoes are a good idea for protecting your feet when getting in and out of the water.
If you go for a Hamman bath a bikini for girls is better than a swimsuit.
If travelling solo paying a single supplement is worth it rather than sharing with a stranger as the twin rooms are fairly small.
The sea kayaking was not as scary or physically difficult (in a double kayak) as I expected so do give it a go if you are undecided. But if you are not keen then ask to go on the support boat and take photo's instead.