We're near neighbours as I'm just a 20 minute walk from the St Pancras terminal.
In 2011 I picked up my then 1.5 year old and took the Eurostar to Paris so that we could get the Jet Airways leased plane used by Thai Airways (at the time lie fat in Business - similar to Virgin Atlantic & Air Canada) and cheaper taxes.
There was very little hassle involved, even as a lone parent with an infant.
We were supposed to fly on to Tokyo from Thailand but the tsunami hit and our family in Japan made clear they wished for us to postpone the trip. My husband joined us in Bangkok instead and we had our holiday there.

Quite a lot has changed since 2011 so I can't advise on best airlines to use, but getting the Eurostar to Paris for a departure from CDG was very simple, preferable I'd say to getting a flight from London and connecting at CDG for an onwards flight.