In reply to teapot:
Just got back this PM. Cheers for all the excellent tips everyone. Thought it might be worth a quick summary and tips of my own now.
Took my 2 girls to 5 venues- including 4 specific kids circuits and Cul De Chien area.
Beauvais Sector Nanville- went on first day- it is an E- circuit and was great - was actually a bit harder than other circuits we did, although plenty that my eldest (just 6) and even a few my youngest (2.5) could do, although not much. Would probably not do as first circuit for under 6's.
Beauville- sector Telegraph- E- - went on last day- was definitely easier than Nanville and my eldest flashed/on sighted all but 2, with two a little reachy for her. My youngest even did a few of these unaided, including one that was amazing to watch. It starts with a narrow tummy shuffle tunnel which my eldest was about to do, when I just checked the ground within the tunnel and found glass surrupticiously buried to cause serious injury! The spot was lovely and I had to drag both away after 30 problems. My eldest also did half a dozen problems in the E+ (salmon)circuit that is there, which were actually better problems. If anything this would have been better as a day 1 or 2 venue.
Canche aux Merciers- this was a quite tough circuit and my eldest needed help on a number of these and also it often involved 2 or 3 problems up the same boulder which was not the case on other circuits and seemed to take a little away from the fun. Was still a good circuit and I recommend it.
Feuillarderie- this is an E-- circuit- only took my eldest here and she did it in less than 30 mins and basically ran around it. A great spot and would recommend as a day 1 circuit and a great spot for 2-5 year range.
Overall it was a great trip and we all left wanting more. Even my non climbing missus was impressed and talked of future visits. Highlight for the kids was still 2 days at Disney, but hopefully layed the seeds for future holidays.
Cheers again for all the recommendations