I am a fan of legal zoom for wills (have referred several people there myself) but trusts are a more complicated instrument. Legal zoom can help create one but the primary problem with trusts comes when people do not know how to administer what they created. Much harder to contest a valid trust than a will. However, the caveat is "valid" trust. With a will the document is the key. with a trust the administration according to the trust rules before death is almost as important. In WA state where I practice we do not allow contests of terms (narrow exceptions for public policy). One can contest the will in its entirety or a trust in its entirety. Hence clauses such as revocation for contest don't play well in WA.
A will does not help avoid probate. A trust does avoid probate and can be multi-generatinal. If your only issue is how to leave someone the least amount of money possible without a contest then a trust is probably the better choice but a will shuld be able to accomplish that. Not sure if that reason is enough for me to recommend a trust to a client in WA.
If you anticipate a family disagreement, I would strongly recommend hiring an attorney and doing the job right. One mistake can cost you thousands of dollars in probate administration and contests.
You should not prepare a trust without a will, or you risk a large part of your father's estate passing under the laws of intestacy. It is so easy to make a mistake, I strongly recommend speaking with an attorney.