You know your audience better thanwe do, but if they loved 42ND STREET they will probably love NO NO NANETTE. I just saw a local music theatre school do this show and it remains a delight in spite of a silly story (but if played seriously as farce it can be funny.)
THE BOY FRIEND starts off with a fun first act but gradually loses steam. (It parodies NANETTE quite a bit, but the score isn't nearly as enjoyable.) MILLIE is even thinner with less of a score. You won't win over many audiences with MUILLIE unless you have a really dynamite cast and a director who can stage it briskly.
LI'L ABNER is loaded with a lot of cornball humour but many of the political targets may baffle audiences now. Great score, though. So does SWEET CHARITY butit is still a problematic show. Audiences respond to the title but the book has some awkward sequences.
Of the 5 you listed, NO NO NANETTE is probably the best choice.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com