Seriously, the best blessings to give the newborn as well as the parents are already in the Siddur and are said as part of the Brit Milah ceremony.
What blessing can be better than saying:
כשם שנכנס לברית כן יכנס לתורה ולחופה ולמעשים טובים
In the manner that he entered the brit, so shall he enter for Torah (learning and knowledge) the chuppah and the performance of good deeds.
I know that you asked about blessing the parents, but when you bless the child this way, you also bless the parents. After all, they are responsible form his Torah learning and finding him a wife so he can get to the chuppah. (Well, OK. a shidduch resume can help, too...)
There are other praises included near the end of the ceremony listed in the same paragraph. But the one I cited is apparently the best one, because it's recited twice.
Everyone answers "Amen" after that, so in a way, everyone is blessing the child and the parents.
The friends and family don't need a blessing and I haven't seen any given. Their presence at the brit itself IS the blessing. Trust me, there are many britot that I couldn't attend and a few among my immediate family where family members and close friends couldn't attend either, usually because they have to be at work early in the morning.