Brides can get so focused on her flowers and decorative arrangements for the church and reception venue that she can give little thought to the flowers for others in the wedding. One rule of thumb that is helpful to the bride as she orders corsages for other family members. That rule is "If the word 'mother' is in the description, the lady gets a corsage. And that means both the bride's and the groom's sides. That includes mothers, grandmothers, great grandmothers, god mothers, stepmothers, and foster mothers. They are all honored guests at the wedding and each should receive a wedding day corsage or wristlet.
The flowers don't have to be elaborate but should be suitable. They don't have to be identical. You may wish to have something special for the mothers, a different flower and/or color for grandmothers etc. Choose soft, neutral colors that tend to go with everything.
It is far better to choose less expensive corsages for everyone than to choose expensive flowers for a few and leave others out completely. The flowers you present to them should convey love and respect for the influential women in your lives. Be sure to include the names of these women in your flower order. Then include one or two extras just to insure that everyone who matters to you is covered.