Future Compound in Polish is constructed as:
1) a future form of "być" + infinitive
2) a future form of "być" + imperfective past tense form.
So here the options are:
1) 'będą czytać' (completely neutral)
2) 'będą czytały' (shows that 'they' are women-only)
3) 'będą czytali' (shows that there's at least one man among 'them')