So the promt is:
Choose one character and discuss what larger point Hansberry seems to be making about the power of the American Dream.
This is my general idea. I chose Mama and how the American Dream is all about being able to do whatever you want regarless of race, gender, religion etc. and through Mama, the author is trying to prove how you are never too late to achieve your American Dream.
I'll create the format once I figure out if my answer is insightful enough.
Any advice or criticism?
Mama certainly seems to be a representative character regarding the power of the American Dream. In addition to suggesting that it is never too late to achieve upward mobility, Mama may also suggest a necessary faith.
Without belief in the possibility of achieving the American Dream, it won't come true. Faith and work and a willingness to take a chance are all part of Mama's character and part of her success.
I agree with #2 in that Mama's decision to buy the house is a lot more about trying to unite her family and stopping them from pulling themselves apart. I think as well that Mama's motivation is based not necessarily on selfish motives of the acquisition of wealth and power, but it is just about love of her family and her desire to provide a home for them where they can grow, just like the plant that she looks after symbolises.
You could also talk about how she struggles with her decision of whether to help Walter achieve his dream by giving him a portion of the money for his liquor store. Is it because she wants him to realize his American Dream, or is it more of what auntlori suggested above -- keeping her family together?
I think Mama is actually a very effective choice for this assignment, since in so many ways she is not the typical "American Dreamer." As you said, she is older than many who aim to achieve their dreams; she is also a widow, which makes her alone in some ways. On the other side of this case, though, is the fact that because she lived through much worse conditions than anyone else in her current household she may be more motivated to want something better than those who have had it a little easier. I also wonder if Mama's motivation is less about the American Dream and more about just trying to keep her family from falling apart. Should be an interesting essay!