Pls how do I know if our file has been transfered to Accra - Your PER should state that your application will be forwarded to a visa office. The exact date it will land in ACCRA, you're not likely going to know, as you wont be updated on this, but you may have a valid assumption that 1 month after PER, Your file is in ACCRA.
Our passports will expire in May 2014 and we intend to renew it in Febuary 2014. -You are free to delay
the renewal of your passport, if you wish, till you receive MR or Till it expires - Whichever comes first. Except you have personal reasons for renewal. Again sending the copies of your renewed passport is not necessary at this time.
Can I also send it if we have the complete amount in our account even if Accra has not requested for it. - You may not send what has not been requested for.
Can we as well send our son's US passport photocopy, we did not send it with the initial application. - I am not clear on this, As you are expected to have included your son's passport number and other info in your application. Is it that your son's info with which you applied was based on his Nigerian passport?