mshieny, I say all you need is tennis shoes. I can't imagine hiking to the top of Belvedere, we rode a scooter and it took quite a while to get to the top!
You shouldn't get motion sickness in the jeeps, I can't sit in the back seat of a car either and I was fine.
I can't remember if you needed adapters for the outlets :(
I would bring a pair of comfy shorts to lounge in the evening. Especially if you have a balcony and plan on sitting on it at night!
I always carry one of those tiny fold-up umbrellas in my excursion bag.