Unless your son can come to the US with a vistor visa then your husband can file I130 and I485 all together to adjust your son's status while in the US, otherwise go with the process below.
He'll have to file I-130 for consular processing. The average wait time to get I130 approved is about 2-6 month (depends on which service center). The case will then transferred to NVC (national visa center) for further processing.
- file I-130 to the USCIS service center designated to your area
-will need copy of your husband's naturalization cert or copy of birth cert and/or copy
of his U.S. passport
-copy of your marriage certificate
-copy of your GC
-copy of your son's birth cert
-$355 USD
When the case is approved and transferred to NVC. NVC will send the following to you and also to your son:
-DS-2032 choic of agent form *this is just to designate who will receive future mails
from NVC.* the best person is the petitioner with a US address
complete this and send it back to NVC
-After NVC received the DS-2032, it will notify you to submit $76 for affidavit of
support review fee.
-You paid the fee online then download and complete the affidavit of support.
Send the affidavit of support back to NVC
-NVC will notify you to pay IV (immigration visa) bill $400.
-You paid the IV bill online then download and complete the DS-230 form.
-Send your completed DS-230 form to NVC alog with the civil documents listed on the
NVC page.
NVC will notify you of any missing documents. If no missing documents, your case is completed and NVC will schedule an immigration visa interview for your son at the US embassy in Brazil. After the interview is set, NVC will notify you and your son with an interview date, time and place along with instructions on where to get medical exams.
Your son completed the immigration interview and obtained a immigration visa. You buy him a airlinie ticket then he can fly over.
Hope this will give you some ideas on how the AOS and consular processing goes.