Covid with a newborn and toddler

My brother has just come home for the holidays from university 3 days ago, it was a requirement from the uni for all students to get tested before being allowed to travel home, he tested negative.

These passed 3 days he has been out to see 2 of his friends, he hasn't seen them in months and he was supposed to go to the movies with them later to watch spiderman but he decided to do an at home covid test and to his surprise there's 2 very clear pink lines, so he has covid and obviously cancelled his plans.

So I know we all need to isolate for 2 weeks but I have a 3 year old and a 2 week old baby, both have been close to him and I'm so worried.

Anything I need to look out for, anything I need to know??

Everyone in the house (my mom, brother and partner) have all had both doses of the vaccine, unfortunately I have not as I was pregnant and it worried me.