Kyushuman -
Definitely call EY to request your seat. AA can give you the EY booking number. You should also be able to book the limo service on the EY site but since you get it with the hotel it might not matter.
The Le Royal Meridien is a nice hotel btw - ask for a sea view if it's available.
The lounge in AUH is great. You'll also find the food on board to be quite good. Steps ahead of AA. The starter bread is delicious and agree on the fruit plate. I've flown this route many times and have never been disappointed. Have a great flight and enjoy Abu Dhabi!