Finding a translator
The role of the translator is, of course, key. Not only must the translator be an excellent translator but also an excellent children's book writer.
For obvious reasons, many publishers tend to prefer to work with people they know, whose quality and judgment they can count on. Failing that, there's always a reliable grapevine (if your French translator can't do the job, maybe there's someone else they can recommend?).
There is also a database of literary translators on the Translators Association website, which can be a useful first port of call.
Translation World Ltd is also worth a look. They are a provider of translations and interpreters and have a database of fully qualified and accredited translators covering all subjects in most languages. All translations are carried out in the translator's mother tongue. Every translator is rigorously checked before and after working for Translation World.
"I tend to explain the peculiar literary ventriloquism of my craft in terms of finding the right voice: I'm a parrot, a bridge-builder, an undertaker, a midwife
and an editor all rolled into one."
Sarah Ardizzone, translator (The Guardian, 2006)
Sample translations
You will almost certainly need to obtain or commission a sample translation prior to going ahead with a particular title.
You may want to look into PEN's new translation grant scheme for translation. PEN Translates! will fund up to 75% of translation costs for selected projects. When a publisher's annual turnover is less than £100,000 they will consider supporting up to 100% of translation costs.