Hi there we stayed in the Grande Real Santa Eulalia in Portugal which I think ticks quite a few of your boxes. We stayed in a 2 bed apartment but you'd actually have plenty of room in a one bed with your DC in the lounge/kitchen or they do interconnecting rooms in the main hotel.
There is a play area and a kids club which looked absolutely fine but DS refused to go to except when it was english kids film time, conveniently at the same time as cocktails for me 
, it was very hot when we were there so I can't remember if the kids pool was heated or not.
It has a spa which offered some treatments at half price. It is within walking distance of the beach - there is a lovely restaurant on the beach side. The only problem with the hotel is it isn't within walking distance of the centre, they run a mini bus into Albufeira and you can get a taxi back for about 10 euros.
Alternatively we stayed at the Iberostar Anthelia in Tenerife last October - hot all year round so no problems with going early, think the flight might be 4 hours, but with a 5 year old you would be fine. Its at Costa Adeje transfer from the airport is about 20 mins, we stayed in a duplex suite so DS slept on a sofa bed downstairs and we had our own room upstairs but all under one key so no worries about him being in his own room. Hotel was lovely breakfast buffet the best I have ever had, they have kids club, heated pool, spa and is also within walking distance of beach. They also have cheesy evening entertainment which DS loved and was nice to relax to with a cocktail ( you get the theme here). I love Tenerife its very relaxing with a young child and the Anthelia is walking distance to shops and restaurant. Unfortunately DS is mini golf crazy - so this year we are going back to the quite nice apartments miles from anywhere that have an en site mini golf course!
Not sure about the noise in either case as I sleep with ear plugs.
Let me know if you want any other info.