Canon law specifies that one godparent is sufficient, but, if there are two, there must be one godparent from each sex:
One sponsor, male or female, is sufficient; but there may be two, one of each sex (canon 873, Code of Canon Law).
This means that you cannot have two godmothers for your child. Only one of the women you have in mind can be this child's godmother. You'll just have to find another way to honor the other woman. One way might be to agree that she will be the godmother if you are blessed with a second child.