Need your help please..
I have booked tickets for Paris to Zurich . We are 4 adults and 2 child (6 and 7 years)
By mistake , I booked all 6 travellers under adult . This is PICCOLISSIMO fare and hence cannot be changed (no refund) .
Is it fine to travel with the tickets ?

My opinion is yes, but its very simple to contact TGV and ask them I have contacted them on several occaisons, they always get back to you in a few days.. so simply contact them for the definative answer.

There is no rule preventing children from traveling with an adult ticket.

Wow, just went on site, saw rates of 150 euros for six adults, at that rate you could easily rebook the two kids if they say you have to, how much more could it be, so don't panic, but serioulsy can't imagine they would care if they are kids since the adult fare is not going to less then the child fare .

And besides, those are the tickets with passenger' names aren't they, so including the cildren's (correct)names?

Don't change anything. You'll pay more if you do. Adult Piccolissimo tickets are cheaper than standard child tickets.