Perhaps the most important idea Albee is expressing in The Sandbox is the disintegration of the family unit. In ages past, it was necessary for the family to stick together. Houses would literally house several generations. The young took care of the old. The old were fonts of wisdom. Age was respected.
In the play, Albee depersonalizes the family. Instead of George and Martha, we have Mommy and Daddy and Grandma. No names, just family function. There is no warmth between any of them.
The sandbox represents the grave and as far as Mommy and Daddy are concerned, this is a good place for Grandma to die.
Edward Albee is well-known as a playwright and is acclaimed for his curiously-named "Who's Afraid of Virginia Woolf?" which obviously alludes to the fairy-tale about the Big Bad Wolf. Other than the link with her surname and her own bouts of manic depression (bipolar disorder), there is little connection between the real Virginal Woolf and Albee's play.
The Sandbox was written while Albee was working on his more popular The American Dream. The Sandbox is a short, one-act play wherein Elbee uses elements which are typically absurd in order to prove his point that life and death (themes) consume us. He chooses a very simplistic way to get his message across. However, it may leave the audience with more questions than answers. In his plays, Albee reveals the self-absorbed existences of his characters. In Sandbox, this adds a disjointed quality to its characters but only in so much as it contributes to understanding a typical dysfunctional family which believes that it functions individually.
Elbee sets out to dispel this misunderstanding of human nature (a theme of The Sandbox). The innocuous characters belie the serious themes which Albee presents. Not attributing names to them suggests that this could be any family and serves almost as a warning. Grandma is the representation of tradition, deserving of respect; she should be not be a burden on her family. Mommy and Daddy are condescending towards Grandma and they effectively leave her to die as she no longer serves any useful purpose. It is ironic that the angel of death is a sunny Californian beach boy. The themes are confirmed through their treatment of Grandma.
People as a product of their society is a theme and also responsibility (or lack thereof). Interestingly, it is left to the audience to decide what the consequences may be for Mommy and Daddy. The circle of life is also a theme and relates to the image of Grandma in a sandbox. As parents, we are responsible for our children and eventually our children become responsible for us.
A primary theme in "The Sandbox" and many of Albee's other plays is the question of how to express humanity in a world that is becoming more and more hardened. As the world becomes increasingly pessimistic, how are human beings supposed to express themselves? The dysfunction of family is also a theme in the play. Death is also an important theme in the play.