My son had RSV when he was 6 weeks. It was terrible to see such a little baby coughing so badly. We took him to the ER. After checking his breathing and everything, they said that there was nothing to do. Just treat the symptoms. Antiboitics don't work for RSV. We just took him home and had to watch his breathing.
They we right. It was a long couple of days but he did get better on his own.
Like other people said, keep thier heads elevated. The Johnsons bath for babies with colds really seems to help with the congestion. Ask your doctor is they are old enough for it. The nasal aspirator that I have is made by safety first. It forms a seal around the nostril and you can really get stuff out (especially after the bath.) I could never get the ones with the pointed tip to work.
Sice your twins were early, I would really watch thier breathing. Don't feel bad about calling the doctor. I'm sure you are not the only first time mom that the doctor has! I hope they feel better soon.