Wedding Gift Requests

We are both in our 50`s and don`t really need any wedding gifts and some people are traveling from out of town and can`t afford the trip and a gift. Can I put "no gifts please" or "The only gift we request is the gift of your presence" on the invitations? Or can I print that on a seperate piece of paper and include it with the invitations? Not sure how to specify that gifts are not necessary.