Eurostar has a service for group bookings, but I’m not sure they’d be able to help you with onward travel from Paris to Switzerland. You could call them
https://www.eurostar.com/uk-en/travel-info/travel-planning/group-travel
Otherwise, I would have thought a specialist travel agency might help. You could book your travel independently, but I wouldn’t want to be stranded in Paris with a large group in the event of delays or disruption, trying to rearrange travel.
It’s also worth noting that - depending on where in Switzerland - you might go via Brussels & Germany to Basel, instead of via Paris.
It’s a longer journey, but might be slightly less busy than to/ from Paris during the Olympics.