Both of my babies were born in July (Melbourne) so I know all about winter illnesses & pregnancy!
I didn't do anything special with my second pregnancy, nor did we refrain from sending DS to childcare. My DS brought home the usual infections & I certainly got the worst of them. I actually gave birth BOTH times whilst having the flu. The first time it was actually the swine flu. I had flu shots, a whole lot of good they did! Unfortunately your immune system is too far compromised by the end of pregnancy for it to combat the nasty bugs.
My advice is to get everyone in your household to take Vitamin D. This year my DS brought home croup & tonsillitis from kinder. My poor DD got both, she suffered terribly! Then DH & I got them. We were literally sick for weeks until our GP suggested taking a Vitamin D supplement. She has mentioned it several times in the past, but I never listened to her. This time I did - OMG we have yet to be sick again & it cleared up all of our winter bugs in less than a week! You can get a kids liquid version at the chemist. We all take it now & won't look back! Good luck!