The key to making your decision is the academic future of your children and your financial means in the future.
Academic: if your children are confident students and that you expect them to make it to an IB with sufficiant points at age 18, then you should probably stick to IB schools - if, of course, you think that you will move often in the near future. It is very difficult for adolescents to change school systems, and changing languages is often a disaster, when they are also expected to learn maths, literature, history, etc. at the same time.
You might want to make a clear planning of your children's future years of studies and the options.
Financial: if for any reason the school fees become unreasonable for your budget (or not paid anymore by your employer), you should think about the options, and they are few: it's normally public school in the local language. This can be OK for younger children, but for adolescents it may jeopardize their future, as they cannot follow the higher (pre-university) tier because of the lack of language mastery. (In Vaud many end-up with apprenticeships because of the language barrier, even if they are intellectually brilliant).
Some private schools offer bilingual options, and there are also bilingual schools; this is definitely a safety net, since the children would be able to study in two language equally. But do check the effectiveness of the langage mastery, since many school say that they are bilingual but the students are not.
On what concerns International Schools in Switzerland, since about 15 years international investment groups have discovered that they could make good profit from them. Some ancient private schools have been sold to the (Hong Kong based) Nord Anglia group, etc.
This does not mean that teaching is bad, and awsome teachers can also be found in very much for profit schools. However, it's like going to a Mariott or a Hilton hotel: you will certainly get the service you want for a very high fee, everything will look fantastic, but teaching is not their only core business.
I agree that the Geneva English School is a very good option; it is not "international" and the academic level is splendid. If you intend to stay in Geneva, this in certainly a good option.
Good luck!