All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
The matter is easy as it is not a condition to announce the marriage for it to be valid; rather, making it public is desirable and not an obligation. Therefore, if the marriage contract took place with the presence (and consent) of the guardian and the presence of two witnesses, then it is a valid marriage even if it is not made public. For more benefit, please refer to Fataawa 83629 and 92096.
The same thing applies to the Waleemah (marriage feast); it is not an obligation according to the view of the majority of the jurists. Furthermore, one may organize it without telling the people that it is a marriage feast.
For more benefit, please refer to Fataawa 98859 and 43516.
Allaah Knows best.