Something that I do: I try to take control of MY alone time when at these family gatherings.
Excuse yourself and go outside every hour or so (as needed) to 're-charge' your brain/emotions/persona. Others may be curious and question your 'need' to separate from the crowd; just be honest... let them know your personality calls for ALONE time to regroup and ask that they please respect your needs.

Believe me.. it will make these loud and 'mandatory open-door' events more bearable.
Good Luck !!!!