What agencies should I contact to find services available for caregivers of famly members with dementia or Alzheimer's?

You're in a good section of the country for help. We can't give links here, but if you google "aging in place Tacoma Washington," it will give you some good links. Much luck to you.

Probably the best place to start is with the local branch of the Alzheimers Association in Seattle. Just google the the organization. They have resources for many types of dementias.