I'd go with


3) EF 24-105 4L - great length but maybe too slow for my kid when indoors


...in conjunction with your flash, you should be good - maybe get a Gary Fong slip on to soften the flash. This lens is great with a decent reach and nice Bokeh. If you wish I can submit some photos to you for you to compare that I have taken in low lightusing flash.


Hope this helps...