I loved using At Mornington: this poem takes you through several stages of life, thus showing how growth and knowledge has forced or influenced a change or come about as a result of change. It also had heaps of great techniques in it.
I also like using In the Park: its simplistic, yet there are several great techniques, you can see the persona reflected upon what they have missed out, and how having children has changed her life, from what well could have been a different path.
And for the third poem, Im tossing up between which one I think you should use. The Glass Jar and Prize-Giving relate to the question really well, so I think they would be a good choices, but you a lot of people will probably choice to do those too, actually all of the poem demonstrate it, maybe you could use Mother Who Gave Me Life because I know in my year, not a lot of people used that poem, and it helps if the marker is reading something fresh.
Father and Child, is a fairly long poem, and would therefore require a bit more of an analysis, otherwise it might seem like you dont have a whole lot of depth if you just skim over it.
For your introduction, it really depends on how your going to answer the question and which three poems you will use, cause your going to need to be able to link and contrast the three poems against each other to show or disprove the question.
Hope that helps let me know if you need more help.