I have no idea what ECV stands for, but I gather you are anxious about your husband's state of health. This being so, having an unvaccinated person visiting is surely exposing him to a risk.
In your place I would regretfully and as kindly as possible tell the family that you and your husband are going to spend Christmas and New Year on your own, as you dare not expose him to the risk of catching covid 19.
Send their presents in good time, or make arrangements to drop them off and say you hope that by this time next year the pandemic is a thing of the past, so you can invite them.
YOu may well be running the risk of offending them, but is that not infinitely preferrable to running the risk of your husband becoming seriously ill?