The choice?
Should you not renew your UK licence nor the class rating but go for an FAA licence then consider; Will the FAA recognise your JAA/UK PPL which is lapsed.
Often in order to gain the maximum exemptions from training on the basis of another country's licence, the licence held has to be current. That question should be asked of the FAA.
You will need to have and maintain an FAA medical to keep your FAA licence valid. FAA approved Doctors in the UK are few and will most likely charge just the same as UK going rates. You have already mentioned the 'Bi-annual'.
You can never forsee problems that may evolve in the future. In my opinion sticking with the EASA/UK system will be the least complicated option. You could always add microlite, difficult to see much difference that matters between many of those and the usual Group A aircraft. At this point with licences being reviewed by EASA letting you licence lapse might not matter or could for the future matter a lot.
You could obtain a NPPL. Cross crediting across classes is now allowed. Only one flight a year on a particular class is sufficient to maintain a NPPL class rating.
Most if not all of your holiday flights will be dual, I suspect, on the basis of how little flying you forsee yourself doing.