Bucks is lovely. Pretty much anywhere round Marlow is wonderful.
I think your choices will depend on housing costs, private vs state schooling, 11+ based schooling or not.
A house big enough for 5 kids will be bloody expensive in Bucks. Perhaps look on rightmove.co.uk to see what you get for your budget that's within a reasonable commute of Marlow. I'd look at how much it costs to buy even though you will be renting initially. No point renting somewhere you can't afford to buy.
Lots of people in Bucks are rich. They send their kids to independent schools. Some areas have lots of independents and not so many good state schools.
Many villages only have one state primary school. Sometimes it is religious (usually Church of England). Consider whether you are happy with that. We weren't.
Bucks has the 11+. There are some fantastic grammar schools. Also fantastic community colleges (new term for secondary moderns). Consider whether you would be comfortable with your kids doing the 11+ and whether you'd be happy with the school they'd go to depending on their 11+ results. Hertfordshire and Berkshire have the comprehensive system and would probably be reasonable to commute from.
We used The Good Schools Guide heavily when hunting for the right village. We had a one year online access subscription. Well worth the money.
Also, train station proximity and local buses. Better in some places than others. See what google maps directions tells you about public transport into London / Oxford and local villages where your teenage DCs friends might live.
We live in Chalfont St Giles. Moved here 4 years ago. We have 3 DC, all primary school. Loads of other incomers live here too. We have lots of friends who have lived abroad or are not British themselves as well as proper locals. I am British but not English. The village has a lovely atmosphere. We felt welcome.