I also do it and am doing Family Relationships with A Doll's House and All My Sons.
I'm struggling to revise for it.
What I done today was read both texts again (third time) and wrote down particular quotes and also the similarities between the texts, as well as making a mental note of the various dialects of the characters. I'm hoping that the major theme is money as there's so many quotes and a lot of contextual knowledge that's conducive to a good answer. For example, Miller was a socialist and it's clear that All My Sons is about capitalism and how it creates insular people and how the war made people more open to views regards society and the 'global village', so to speak. Similarly, A Doll's House is pervaded by money issues and troubles, most explicitly Nora's trouble with her father, Krogstad and Torvald. Nevertheless, there are also minor characters (Kristine and the Maid) who had to give up things due to money-struggles. There are further issues regarding society as a whole.
The law is another crucial theme. Both Torvald and the minor character Frank have a strong view of the law, believing it to be crucial (Frank mentions it somewhere), as well as Krogstad ('the law takes no account of motives'). On the other hand, Nora, Keller and George have a dim view of the law. Nora is shocked that her situation will not be regarded ('then they must be very bad laws') whilst Keller is more concerned with money ('I made you money, what more do you want?'); this could also be reflected in his discursive nature of Bert and the jail game at the start of the play. George, similar to Nora, is a bit sceptical of the law despite being a lawyer ('outside, the law doesn't make much sense').
In my opinion, the final major theme in both is the relationship between father, son and daughter. This theme is particularly evident in A Doll's House ('you're just like your father, you have his irresponsibilities'... or something) as Torvald, upon discovering Nora's lie, won't let her look after the children, and his comment regard 'poisoning' their home with lies. Chris also feels guilty about Joe Keller's crime; he feels he must run away, disregard the business, 'dirty money'. 'That money has blood on it'. This can also be said for Annie and George, and the Maid and her children, who she had to give up.
There are many other themes evident in both, as well as on their own. For example, both deal with the issues of women, especially A Doll's House which is easily comparable to All My Sons. Contextual factors are also rich in both, for example, post-war America, 19th century Norway, women's rights, rise of socialism and shared responsibility and scepticism in religion.
I don't think there's much excuse for anyone doing these particular plays to struggle to write something.
Also, I'm sure your teachers have said but remember to include things about the nature of the plays - they are to be PERFORMED, not read, so you will get credited especially for things like comments on the stage directions, former plays, audience of the plays, both now and then, and the variety of the performances. For example, the first performance was received with disgust (see 'alternative German ending') and yet now, to make it more interesting, performances actually have Nora dressed as Lara Croft, in some she shoots him and some versions are even set in the future. My next bit of a revision (and hopefully last) is to go over specific performances to bring in and remembering specific quotes. These are an easy mark.
What I'm struggling with is the unseen text (which to me seems like a bit of an 'add-on' or after-thought). The focus this year is like structure, language and something else. I'm not really sure what I could write or how long it should be.
My teacher all year has complimented me on my writing, analysis and all that, but because of this I really have no idea what I should do. I just 'do my thing' and get a well done. I hope that's because I do it naturally rather than he's just an easy marker or something.
Also remember you only get 10 marks in each for your language/literary terminology. It's not crucial to spam your answer with words like adjective and 'diminutive' and stuff like that. I guess my advice for what it's worth as I'm at the same level as you guys is to just open your mind and don't be restricted too much, just explore the texts deeply as well as widely, taking in all the contextual factors as well as literary and linguistic terms to try and explain and support the point you make.
And most of all, good luck I guess!