Agreed with everyone else! I've been on Humira (plus AZA - so that's double a lowered immune system) for a year now and haven't had a single cold!
Wash your hands frequently. Maybe try to stay away from children's faces, so in case they sneeze/cough it won't be directly in your face. If a child has a noticeable sickness, there's nothing wrong with wearing a face mask for a while.
I would also make sure you are taking good supplements. A healthy dose of vitamin D, and C keeps your immune system strong enough to fight off normal things. Vitamin deficiencies can leave you susceptible to catching bugs more easily too, so supplements are a good idea.
Don't stress about it too much. Just focus on how AWESOME you are going to feel very soon!