You're right to be concerned, since the vulva and opening to the vagina can be easily irritated--and more so after menopause without estrogen therapy. Vitamin E oil can be used both for massage and lubrication. Liquid Silk is a lubricant that many women find soothing applied in the vaginal area. Most things that are flavored or heavily scented have the potential to be irritating to that delicate skin.
We've also liked Zestra, an arousal oil designed to use externally on the vulva. Its warming characteristics can be helpful in "reawakening" sensations as part of an intimate massage. As with any warming product, try just a small amount first to be sure it isn't irritating.