It is never appropriate to request a gift of any kind for any occasion. A gift is the sole choice of the person or people giving it.
Many engaged couples have asked how they can let their guests know their preference of money over gifts. It is inappropriate for the bride or groom to inform their guests of their gift preferences. It is also inappropriate to have any such wording or enclosure in the wedding invitation.
The bride and groom must rely on their network of close friends and family members to discreetly inform their guests of their gift preferences.
This same rule holds true for gift registries. Never enclose a list of where the bride and groom have registered in the invitation. If wedding guests would like to know where the bride and groom are registered, they should contact a family member of the wedding couple to find out.
A wedding guest is never obligated to choose a gift from the registry. Again, the gift decision is their choice.