I am the mom of b/b twin five year olds. A friend (triplet mom) advised me to have my ducks in a row by 28 weeks. I am glad I did, as I was put on bedrest at 28w2d.
1. Definately get a referral or make an appointment with a perinatologist. Multiple pregnancies have a lot of issues and a peri has the additional training to deal with them. My peri and OB worked together. The peri monitored the babies, the OB monitored me. I was able to go 34 weeks despite lots of complications because of the excellent prenatal care I received.
2. If she wants to participate in decorating the nursery, buying clothes, attending showers, etc, get it all done by 28 weeks (maybe even 26 with triplets)
3. Organize. Assign each baby a color. It makes it so much easier to tell burp cloths and bottles apart. One of my sons was assigned red the other blue. I even dressed them accordingly for the first year or so, and it was easier for everyone to tell them apart once they knew Twin A was red, Twin B was blue. I also kept charts on when each twin ate, how much, meds given, diapers, etc. I had a lot of helpers, and this way nobody missed a feeding or was medicated twice.
4. Ask for help. I did hire someone to come in and clean at 20 weeks as I was too big to do anything at that point. That in itself was a big help. My mother also came and spent weekends with us once the twins were born so that my husband and I could get a good night's sleep two nights per week. BEST GIFT EVER!!!!!!!!!!!!!!
5. Read Dr. Luke's book "When You are Having Twins, Triplets or More". Excellent advice, especially the diet section. You have to eat a lot early on, even when you don't want to.
6. Rest and get off her feet as soon as she can every day.
7. Keep a journal!
LOL, she can let us have one or two! 
