My parents are in their late 80's - still mobile but this needs to be gentle.
Bristol or Cardiff airport. Heathrow at a push. 1 week, 10 days max.
2 hrs air travel.
Car hire the other side.
Warm, not baking, villa with pool.
Beach holiday not necessary but nice coffee shops, restaurants, some small shopping areas nearby. Places of interest to visit.
We've visited France loads (love the markets) Portugal too. Happy to return to these areas again.
Budget isn't great so I need to be thrifty!