The Italian Dolomites are littered with Via Ferrata which are now modernised and maintained allowing quick and easy access via cables and ladders fixed to the side of the mountains. Multi day tours can be made using huts and taking in old fortifications and of course the views.
Within 30minutes to 1 hour drive from Chamonix there are various Via Ferrata (some old and some modern) which make a fantastic activity in their own right for groups and families alike. The nearest to Chamonix is at Passy, just down the valley, with a grade of AD+ (technically easy with enough exposure to make is a little scary). It takes 2-3 hours to complete and covers 400m of rockface with 200m of ascent.
Your Mountain Guide will provide all the specialist equipment required and guide you through the experience while making sure that everything is safe.