That's a pretty big search area!! I've heard it said more than once that there are no bad schools in Bucks. Which of course isn't true - but on the whole Bucks primary schools are very good. Whether that's due to educated and supportive parents who want their child to get through the 11+ is a whole other debate...
Anyway - it sounds as if you need to be picking your area based on the non-grammar secondary school you want your son to go to. I'm no expert in secondary schools at that end of the county, but I consistently hear good things about Waddesdon so that would be my starting point. My understanding is that it's heavily over-subscribed so you'd need to choose where to live quite carefully.
High Wycombe is very very mixed socially and I THINK many of the non-grammar schools struggle - an acquaintance told me she'd returned to work so she could pay for private school if her daughter was allocated Cressex as there was no way her daughter would be going there. And I know there's masses of new housing going up round Aylesbury. A huge new primary school has been built but I haven't heard anything about new secondary provision, which presumably means that the existing schools will be very stretched.
Wendover - the John Collet school had a rough Ofsted last summer but I heard on the grapevine that the majority of the school is absolutely fine, it's just Science that let the rest of the school down, as in common with many schools round here they struggle hugely to recruit science teachers. Science is a core subject so the whole school was down graded to match the assessment of the science department, even though there was extremely good practice in other areas of the school. However, the leadership are now under huge pressure which is being passed on to staff. I've heard (don't know how accurate this is) that Holmer Green secondary (not far from High Wycombe) is in a similar situation, although I don't know the reasons for Ofsted down grading them.
The problem with being in a grammar school area is that although the grammar schools are very good, the majority of children who don't go to grammar school are more likely to be placed in a struggling school as many of the brightest, most motivated pupils have been creamed off. On the fringes of the county many parents avoid this by sending their child over the border to the comprehensives in neighbouring counties. So Lord William's school in Thame might be worth a look as Thame isn't that far from Aylesbury. Or if you are the other side, Tring would be worth a look (but I know absolutely nothing about schools there).
The other two non-grammar schools I've consistently heard good things about, with parents actively moving to be near enough for a place, are Chalfont Community College (Chalfont St Peter) and the Amersham school. Neither of which are in your search area, but I thought it was worth mentioning them!
Good luck. In your position I'd start by looking at Waddesdon for secondary. Once you've sorted out the secondary you fancy, then you can look at primary.