for swimming Leatherhead is closer to Cobham and has a very well regarded swim team
No state school is allowed to be academically selective (in Surrey anyway - very few Counties have Grammar schools but best not confuse you further with that one!). I'm afraid I would have to differ with LIZS on the catchment issue - George Abbot and Howard of Effingham which are two of the best performing state senior schools in your proposed area definitely have very tight catchments which has a knock on effect on property prices!
At the ages your children are it will be fine because none of their cohorts will have chosen their GCSE subjects yet. However because you are applying outside the usual timescale for senior schools you will not necessarily have much of a choice for state schools. The obligation is for the Council to offer you a place at ANY school that has the space, not necessarily the one you want. If you are Catholic then this may help as there are some well regarded Catholic schools in Guildford and Leatherhead.
There are a lot of Private schools in easy reach of Guildford, Cobham, Woking etc - have you got the Good Schools Guide? That's a good place to start for independent schools. Some offer IB alongside A levels.
ACS is actually closer to Esher than Cobham, it is very "American" and on a very busy road at school times. The school holidays also do not chime with UK schools which may have an effect on extra curricular activities if you plan to travel - this affects some girls my DD dances with for example.
I have a friend whose son plays ice hockey at Guildford - beware as it does involve a lot of travelling all round the country most weekends as Ice Hockey is very much a minority sport and so there are few teams to play against!
Many more kids these days go to the US for Uni after doing GCSE's and A levels - they are well regarded qualifications and sometimes earn the students credits before they even start as they are above the High School levels in some subjects. It will obviously cost squillions though unless you qualify as a home student but you will know this already.....
Commuting as others have said is very straightforward by train but expensive - several thousands of pounds a year and frankly soul destroying. Woking is quickest of the places you have mentioned (and most frequent trains late at night coming home) but the least aesthetically pleasing in my opinion!
Hope that all helps!