I think you will be fine at either hotel, but I am less experienced with the Athénée.

Anantara Siam is my regular hotel and I absolutely love it. The club management is the best of the best. You will not want to skip dinner given the quality of the food, but you can order room service from the full menu of any restaurant as well. The club service and canapés are also very nice.

The swimming pool is of a standard rectangular design. I particularly like it because unlike some of the fancier swimming pools around, this one actually has a deep end that you can dive into - which is very refreshing - and it is also possible to swim laps. The poolside service is great, and they have children’s activities and babysitting available.