oscars restaurant next door to coronas playa hotel,cant go wrong,food service ambiance etc is all lovely and if i remember right they have a small childs menu too,but even if they dont i have seen children in there,if you speak to them before hand they might even arrange a birthday cake etc.
also momarte french next to los molinos,all of the above and lovely owners,very child friendly even tho it's a 'grown ups' restaurant.