Assuming that you hold UK passports, you're not eligible for the 'green card lottery' (which is only available to nationals of countries which are under-represented within the USA).
So that basically means that you've absolutely no chance of being allowed to emigrate to the USA unless:
(i) you've got close family members there; or
(ii) you've got specialist skills or talents which can't be matched by those of a US citizen (e.g. if you're a world-famous English character actor); or
(iii) you've got relevant professional qualifications to advanced degree (masters or doctorate) level.
See here for details:
http://www.usembassy.org.uk/cons_new/visa/iv/i ndex.html
Chris