You can’t directly share just part of a tree on Ancestry—but here’s a workaround: Export your full tree as a GEDCOM, then re-import it as a new one. In that new tree, delete everyone from your side. Now it’s just your husband’s family! Share it via the Tree Settings > Sharing link, and invite his relatives as Editors so they can add details. Living people stay private unless you allow access.
For records, suggest FamilySearch (https://www.familysearch.org) or YourRoots (https://yourroots.com/search-record/country/united-states).
It’s a great way to let them explore and grow the tree safely.