My advice is: Become familiar with the RMV map. Eschborn Sued is connected by two local train lines (S-Bahn), S3 and S4. They run every 15 min. In case his work is really close to that train station, taking that train is a good option. Some of the office buildings are 15-20 min walk from that train station which sucks especially in the winter, so he should check that out.
Large parts of Eschborn are not very nice, I wouldn't say ghetto, but I wouldn't consider living there either.
Of the areas you have mentioned, I would definitely consider Roedelheim. It is an up and coming area but closer to the city and better connected to transit and has several nice pockets. For a family, Bad Soden and Kronberg (at the terminal of the S3 and S4) are nice but definitely on the pricier side. And unless you lived very close to the S-Bahn stations, the commute would be longer than your husband desires.
For travelling around and the destinations you have mentioned, the train would be convenient (
www.bahn.de). If you are staying one year, a Bahn card (currently 240EUR or so) will quickly pay off. Gives you access to always 50% off and flexible tickets. The "normal" fares are fantasy prices and a rip-off but with the Bahncard you will be ok. There are also tickets to be purchased abroad (e.g. 4 days of unlimited travel within 10 days and so on) which are quite reasonable and may be worth looking at. Note that you can't purchase them in Germany.
Also, since Frankfurt is such a big hub, there is a lot of competition and flights usually available at very reasonable rates if you are able to book in advance (e.g. the 99 EUR deals with Lufthansa to several European destinations).
It is very possible to get around Frankfurt without speaking German. However, every little attempt will be much appreciated by locals so don't be shy to give it a try. If you arrive with practically nothing, chances are, you will be leaving with your German at the same level. (I've seen this in many former colleagues). If you have some basics, you will be able to practice a bit and soon get better. (I have also seen this and was quite impressed.) I think that is especially important for the kids. With a bit of a basis, they will be picking it up in no time.
It's been a couple of years that I left Frankfurt so a lot of the additional information I'd have is not current anymore.
I suggest to register on internations.org and ask your questions in the local community. There should be plenty of people in the same boat who can hopefully help you out and also advise on schools etc.
Good luck with everything and hopefully a wonderful experience.