Traveling w/ children

Location: Washington State

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I'm planning a cruise trip that includes an international stop (Canada). I have two children that I have sole legal and physical custody over.

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My research says I only need their birth certificates, state IDs' and possibly a copy of the parenting plan to travel with my children, but can anyone confirm that? The issue is my ex has gone completely no-contact and I don't even know where she is at this point, so if I need to get her permission I wouldn't be able to regardless of the fact she wouldn't give it.

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Thanks.