We're giving boutonnieres and corsages to our immediate family members. Parents, siblings and their spouses. We would give to grandparents if they were still around. It's less of a gift and more of a symbol that these people are your immediate family. That being said, no harm in giving granny a gift if you want to for whatever reason.
Family attending is enough to give a corsage or for suit (men). They are there for you and to know who is family from friends and other guests. Its the thought that counts for what your doing for her and everyone else.