Just to echo CL300, my daughter started in the local village school at age 4 and was coping fine with the French language in a couple of months. She was completely fluent in 6-8 months and now of course refuses to speak in French to her parents because she finds our accents embarrassing
. If your lads are 3 and 5 then they will be absolutely fine I'm sure. The schooling seems better than in the UK with more emphasis on the basics. All the kids seem to be very polite and well disciplined at school (and outside it to be honest). If you are here long term then the secondary and tertiary education are also good.
On the other hand I have a couple of friends living in NE Spain, around Barcelona, who have not had good experiences with the local schools and funnily enough one has decided to send his to a private French school nearby.
The bottom line of course, if you need further convincing, is that moving here and not becoming bi-lingual would be denying your boys one of the really great things about living abroad and something which they will find really useful in later life.
By the way, would the well known firm be NetJets?