We stayed there last year when our son was just 2.
As you say the resort is very steep but this didnt prove a problem for our son. I The only issue I would say was the marble floors in the villa could be a bit slippery at times and the railings outside the villa were quite wide so we had to be very vigilant. The villa we stayed in had a 2 winding staircases and as long as you are watchful these are ok.
The top pool with the slide is great, and our son loved it, aswell as the lager pool further down.
My own negative would be that there isnt anything for little ones to do other than be in the water, so you need to come prepared with a host of activities for indoor time.