We can only generalize on the current conditions. As others have pointed out, who knows what things will be like by Fall. My guess is that entry testing will be gone by then, but there really isn't anyway to predict with accuracy what the government will do.
Under current conditions you could possibly get back to the USA faster from the UK than from France. UK doesn't have a mandatory quarantine but asks people to self-isolate. France currently requests 7 days isolation. In either case you require either a negative covid test or a certificate of recovery to enter the USA. A certificate of recovery can be issued 5 days after a confirmed positive test for a person who is asymptomatic or having decreasing symptoms. Italy currently has the strictest requirements of all these countries in regard to quarantine.
If you have purchased travel insurance, many of the companies include quarantine coverage in their policies. You would need to do the research and make sure you were covered by the policy you purchased. This mitigates the financial risk by quite a bit.
I think the real issue here is the amount of stress that this might generate for your husband. It is not a vacation if you end up spending the entire time worried about what might happen at the end. There are certainly many, many places you could take a vacation to that would not involve this sort of stress for him.