In reply to moreno:
Yes, it is possible. ( With the caveat that I obviously don't know you and your children and your capabilities ).
As others have suggested you would be better off walking from the Torino side back to the Midi as the narrow ridge at the Midi end is less scary for most in ascent than descent. It will probably take in the region of 4-5 hours.
It will require stamina, a good head for heights and some acclimatisation to ensure it is enjoyable rather than a lung heaving experience. Roughly half the journey is downhill, the second half back up is a long and continuous slope.
As others have suggested a trip down the ladders ( easy to protect with ropes if required ) to the Mer de Glace would be a great way to experience a dry glacier, get used to walking in crampons and some scrambling about on spectacular ice features.
Another option may be to go to Zermatt where there are some good high walks to get some acclimatisation and then consider a trip up the Breithorn. This is a short, easy 4,000m peak with spectacular glacier scenery.
In the Chamonix area another acclimatisation option on a spectacular glacier with a small peak might be to go up to the Albert Premier hut for the night then next day follow the glacier to the Tete Blanche. Have fun...