@grouchox It depends on the age of your older child, and how used you are to run into a dense car traffic, but we have a pick / drop bike system (velib') which is ok with stations everywhere. Or simply have a one week pass for our public transport system (see RATP) if you plan to make more than 3 travels a day. It will include bus / tram / metro / local train (RER). You will likely ave to use RER if you land at CDG airport.
@certainlytwice Thank you. I'll give the RATP a go, I think. On a side note: we arrive by train. The last time I flew in, that took longer door to door from where I live ( a bit surprising, and not entirely a compliment to CDG).