WOW! Don’t know the Wal-Mart brand, but Ensure Plus is good. If you check the Wal-Mart Nutrition Facts label against an Ensure label and the percent RDAs are the same, the Wal-Mart brand is probably OK. Also, read the list of ingredients which should be mostly milk products, sugar, oil (to increase the calories) and added vitamins.
You are right about the excess Vitamin A. Most prenatal vitamins though only contain folic acid, iron, and vitamin C to improve iron absorption. Most medically recommended liquid supplements have 100% of the RDA in 1800 calories or about 1200 ml (or about 8 cups). So between pre-natal vitamins, liquid supplements, and her regular food, she is probably OK as long as she doesn’t take beta-carotene or another Vitamin A supplement.
Check out the Healthy Body Calculator. It will calculate the calories Cyndee needs for pregnancy and predict a healthy weight gain. However, I do not know how the calorie needs increase with multiple babies. Also if she decides to breastfeed, it will calculate the calories for lactation. But again, I don’t know how the calorie needs increase with breastfeeding multiple babies. An average baby consumes about 1 quart of breast milk per day.