If you are A subscribed ancestry member, you can indeed have a public tree on there, and your family can view it freely, by invitation, and a password, which Ancestry will instigate for each person you invite, All you need to do is send them an official email invitation directly from your tree, (under Share Your Tree), Ancestry will provide the password and registration info.
From there, you fill in the email address etc of your relative, or anyone you want to share your tree with, there's even a space for a wee note to them.
They will however, have to register first before being able to access the tree - (NB Not subscribe).
You also have options as to whether you allow individual relativesto view living people on your tree
I've sent invitations to several of my relatives - works well.
Best to invite them as a Guest. There is also an option to invite them as an Editor, which allows them to edit your tree, change things, add people, photos, stories etc, but unless you are very confident of their computer skills, and attention to detail - Guest is by far the safest bet.
Good luck with whichever avenue you choose anyway, I'm sure your relatives will be pleased.
