If Stonehenge is busy with tourist buses then try Avebury ... atmospheric stones and the old village give a real feel for how the landscape has been inhabited for millenia ... and you can just stroll through them at will which is a plus. Personally my favourite of the two on balance

As petrolheads try a race day (or part) at Shelsley Walsh .... oldest motorsport course in the world and car heaven on a sunny day ... British Hillclimb Championship round on June 3/4 I think (some of the fastest cars/drivers in the world doing jaw-dropping speed up what is pretty much a country lane) ... or if there's a classic weekend in your time frame that might be good ... place oozes atmosphere and history and you're right in amongst the cars and drivers

K