This is an easy step for a bit of additional peace of mind. A temporary travel will before a vacation can help people know your wishes if anything should happen to you.
A temporary will is not a replacement for a permanent Last Will and Testament drawn up with a qualified attorney at law. However it is usually considered legal and binding. When my wife and I travel on occasion without our kids we will always draft a temporary will in case of an auto or plane accident or something that would hospitalize or kill both of us. We don't tell our young kids about it, we don't want to worry them, but leave it with a parent, sibling, or close friend. Usually we leave it with whomever is watching our kids.
A temporary will should be dated. It should spell out who you would like to be in charge of your children if you both should die. It should tell where important papers are and where a primary bank account is and who (by full name)should have access to those funds and documents in an emergency. It can also address your wishes as far as medical care. You can authorize someone to make medical decisions on your behalf if both you and your spouse or companion are unable. Where we had relatives of a different faith we even spelled out the church we desired our young kids to attend until they were old enough to decide that themselves. They fully understood and agreed.
This type of will should be signed and dated by both of you, and ideally a witness or two as well. Once finished seal it in an envelope and leave it with instructions. It is of great use and will hold weight with a probate court if you don't have a permanent will. A recent temporary will can actually hold some weight over a formal legally drafted will, as it would be of a more recent date. Use this if you need something clarified before a trip. If you would like to notarize your signatures that is an additional safeguard that your wishes will be followed but not necessary to make it valid.