experts either too much since they've got enough going on, but I'm asking them the same sorts of questions just to be sure we're doing the right thing and can socially connect with them and the G-kids, which thankfully we've been able to do (hugs, etc.).
Back to the Bidens & Carters...the determining factor is being "fully vaccinated"...not whether they are old...or 'Really Old'...a small group indoor gathering without masks or social distancing is A-OK and encouraged...what a medium or large group looks like is not clear...so many variables...left to 'reasonable judgement' (my term). When it comes to outdoor masking, you are entering an "unknown environment" as to who is vaccinated or not...caution would dictate wearing a mask...if only to convey a good example...i.e. "When in doubt...wear your mask" (again, my words only).
Speaking specifically wrt the Bidens, the photo doesn't show where they were headed next...if it was to a larger gathering, or mixing closely with others who are not known to be fully vaccinated, they were likely doing the right thing.
Given the CDC guidelines, you'd have to admit that the Bidens did not cause harm with their examples. BTW, the more I read about masking (e.g. Baron's MIT Report...I'm not 'ragging' on him...this time) the more I am impressed with the role/effectiveness that small mitigating factor has.