Hi there
Sorry I can't offer advice on play areas for the kids,but you'll be right next to the beach,in a lovely area, where you're staying.
Right opposite your apartments,La Trattoria (which is one of the Restaurants belonging to the Parque Santiago complex..no3) is very family friendly,as is the Bier Pinte a few yards along the road, also the Plaza Cafe in front of Parque Santiago 5. The waiting staff at each of these places will make a huge fuss of the kids. Always noticed they absolutely adore children...especially the little ones.
There are plenty of Restaurants in the surrounding area, and any time we've been,plenty of kids dining out with their parents. Hope you have a great time.
Have a look at
http://www.parquesantiago.com
You'll get an idea of some of the Restaurants/Cafes that belong to the complex on here.