We are taking our family of 8 adults to Paris the end of June 2016. We are looking for the best value in either an apartment, B&B or hotel. I would love some suggestions!
Look on a site like Vacation in Paris that has a good reputation for a place that will sleep 8. An apartment is the right idea for a group this size because you have common social space and a kitchen for breakfast (you will save maybe 80 Euros a day by just heading to the local bakery and picking up breakfast bread; a baquette is about a Euro, croissants not terribly expensive; orange juice and coffee will be much cheaper at the grocery store than by the glass; you can stock the refrigerator with yogurt, cheeses, wine etc even if you plan your main meals at restaurants. 8 is a large number as Paris apartments tend to be small but if you search VRBO, AirBnB etc you will probably find something.
And some gratuitous advice that we always follow when traveling with family and our groups are not as big as yours -- plan to split up for activities. The odds that 8 people will want to schlep together to do the same thing every moment is zero. By splitting up occasionally into 2 or 3 or even 4 groups and then coming together at planned times to share your experiences you will probably have more fun than death marching everyone through the same itinerary. I don't know if the 8 is a nuclear family that lives together through the year or extended family living in different places. We had grown kids who didn't live in our town and so teaming up in pairs to cook, or take in a museum or whatever gave us a chance for quality time one on one. It is also something we did when our children were young so that parents each had quality time with each of them. 8 people is a lot to go anywhere; organizing different excursions for different interests while coming together for the Eiffel Tower, or Seine Cruise or other thing everyone wants to do will probably improve the experience.
A tip about the Louvre. The Louvre sits at the head of the Tuilleries which is a lovely park with lots of chairs, fountains where you can rent toy boats to sail, several nice playgrounds including pay trampolines and in late summer a carnival. If there are kids in the group, you can start in the Louvre with the highlights they are interested in and then one adult can take the kids into the park to play and snack while the others continue with the museum. You can also trade off; the ticket is good all day so the parents who left with the kids can be relieved by one of the others and go back in if they like.
Vacations in Paris has one apartment that sleeps 8. Check out their website. That unit is pretty pricey but hopefully you're splitting the cost between a few groups. It's 4 bedrooms. $700 per night. Here's a link:http://www.vacationinparis.com/listing/336/upper-marais-4-bedroom-duplex
What is your budget? And do you want to be in an particular neighborhood. Without knowing those two things, it's hard for me to make specific suggestions. And definitely if you want an apartment, you should get on this right now. In March 2010, I wanted to travel with a group of six to Paris and did not start looking until the end of February and had a very had time finding a place to suit us. We wanted three bedrooms with no one sleeping a living room. I can only imagine that with 8 adults, the search might be more difficult. Ultimately we found a place with ParisPerfect and it was great but quite expensive. Franky, it was not less than 3 rooms in a hotel but we wanted to all be together in a shared space and had some food issues that made us need to be able to prepare some of our own meals. Depending on the budget, you may want to consider getting 4 double rooms at a Citadines if you want a sitting area.
The Hotel Latin Excelsior near the Sorbonne and Pantheon has a family suite that sleeps 5 as well as quad, triple, double and single rooms. It's a nice place.
Vacation in Paris also has two apartments in one building just off Rue Cler that together will sleep eight. They are the Garden Studio (#2) with queen bed and twin trundle beds, and the Eiffel Hideaway (#56), a one-bedroom with sleeper sofa in the living room.
http://www.vacationinparis.com/listing/56/eiffel-hideaway-one-bedroom
Together they would be less than the four-bedroom apartment posted above, although you will have people sleeping in the living room, not all in separate bedrooms.
Vacation in Paris is an American company with offices in New Jersey, so you can easily call them and discuss your needs. They may have other combinations ( 2 apartments in one building) that would suit your group. It may come down to what is available on your dates.