I would think it would be perfectly appropriate.
What is most important in making any sort of offering is that the offering be something meaningful and that it is done with specific intent to honor the Gods. I know people who choose to donate blood as a form of offering to their Gods. I know others who pick up litter along the highway, plant a tree, or do some form of service as an offering.
To my mind, it is more the spirit in which the gift or service is given that is important than the actual form of the offering.