What about the new Spiderman musical? My good friend is playing the Green Goblin, and he is just raving about the whole performance. They are in previews for the next 6 weeks, so I don't know how that would fit in with your timing. The music should be right for your sisters. How can you go wrong with Bono and The Edge? I saw a clip of it on 60 Minutes Sunday night, and really wish I could get to NYC to see it!
Is Shrek still playing on Broadway? I haven't seen it, but heard it was fantastic.
I did see Jersey Boys on tour..........incredible..........& I had no interest in seeing it. I'd see it again in a heartbeat.
Unfortunately, Shrek closed a couple of months ago... Which is a shame really, it looked amazing.
I've heard The Addams Family is supposed to be really good. Or how about Mamma Mia?
I don't think you could go wrong with anything you see!
Good luck finding a show to see wish I could head down to New York! 
I saw Addams Family last week and it was really good. Nathan Lane is hilarious in it. My friends and I went after we couldnt get into Elf, we didn't know anything about the plot or songs but it was fine. We loved it.
Rock of Ages would probably really appeal to the 40 yo and the 18 yo would probably enjoy it too.

Okay... I am going out on a limb here but what about Avenue Q? It is playing off Broadway as far as I know. Now... not knowing what your or your families' tastes or tolerance for rude humour are... it is a bit of a risk for me to suggest. We took our then 14 year old DS to see it when it came to Seattle a couple of years ago and we all loved it. But you have to be prepared for naughty language and puppet sex!!!![]()

Thanks for the suggestions but my younger sister and I have seen Wicked already and my older sister wants to save it to see with her DD. Sorry, I should have mentioned that! Jersey Boys I forgot about and have heard wonderful things about it! But, will my 18 year old sister appreciate Frankie Valley?![]()

Rock of Ages would probably really appeal to the 40 yo and the 18 yo would probably enjoy it too.
