Family of 5 - Paris accommodations and airport transfers

With 5 people, 3 of them lil' ones, a taxi would probably work best to get to Orly.

The only hotel I know of that packs 5 people in one room is Marignan in the 5th which is a good location; it is a bare bones budget hotel but does have at least one family room that accommodates 5. Look also for suites in other hotels. And of course there is the option of an apartment. Yeah they are pretty much all illegal, but they do solve your problem. Take a look at AirBNB and agencies like Vacation in Paris. Another option is two rooms with the parents split up which is not that fun. There are almost no hotels that will allow 5 in Paris and they will turn you away if you show up with more people than booked for.

The only sensible way to get to and from the airports with 5 people is by cab; the dispatcher at the airport (official taxi queue don't go with anyone who offers a taxi) will match you with a cab that accommodates 5. The cost is fixed; 55 from CDG to the left bank and 50 to the right. From Orly it is 30 to the left bank and 35 to the right. You pay 4 Euro extra for the 5th passenger. the fixed fee covers 4 people and luggage.

For return to Orly you would order a cab the night before from G7 making sure they know you need a van cab to handle 5 persons. There is an added 7 Euro reservation fee. This is cheaper than public transport to Orly.

I would rent an apartment. That is what we are doing and we are a family of 4. We rented through VRBO. Gives us more space, opportunity to have some meals 'at home'
I would pre-book a taxi to get to the airport

Hotel Marignan is a good rec. i stayed there for 6 wks many years ago and stopped in last week just to see it again. The owner, son of the owners when I stayed there, could not have been nicer. He was very happy I stopped in and took me on a tour. They have a kitchen and a free washer/dryer (looked new) for hotel guests to use. It's in one of my favorite neighborhoods, very close to the river and Nôtre Dame. I recommend staying here.
We've rented apts 3 times and the first two times we were very pleased and enjoyed the apts. This last time (3 wks ago) the apt was horrible and filthy so we refused to stay and went to a favorite hotel. Apts do not always work out well.

Hotel Excelsior Latin has three types of rooms that sleep five. All are two rooms that open into each other. For example, the family suite is 1 double room with 1 large bed and one adjoining room with 3 single beds. Hotel Left Bank Saint Germain has an apartment suite that sleeps five.

I would not rent an apartment on your first visit, because it's virtually impossible to assure whether or not it will be a legal apartment.
If you are on a budget, you will not find two bedrooms with "real beds" for your family or two full bathrooms, virtually anywhere in Paris.
Apartments in Paris do not have air-conditioning - something that most people take for granted.

If you are staying less than one week, you might find that the owner/manager prefers to rent for a longer period of time, and you might face a last-minute cancellation. This would mean that you would have to scramble to find accommodations by yourself.

In addition to the hotels mentioned above, here are some more options:

There are legal apart'hotels which will give you 24/7 front desk service, cribs if you need them, and whatever else you need. There are also kitchens in the rooms. Some have air-conditioning, and others will have fans for your use.

Citadines and Adagio are the leading chain apart'hotels.

You can sometimes find adjoining rooms - especially if you book now - which will give you the option of having more space, real beds or comfortable sofa beds, plus an extra full bathroom and another kitchen.
If you can't get adjoining rooms, all is not lost -
If the kids are apprehensive, I'd just let Mom stay in one room with some of them, and Dad stay with the rest. Then they can switch, if they want.

It really isn't possible to stay near all the things that people want to see, since many things are spread out.
You should opt for a neighborhood with good transportation options, such as the 14th, 11th or 12th. There are plenty of Citadines and Adagio apart'hotels in these neighborhoods.

There are flat fees in effect for going to Orly airport by regular Parisian taxi.
Depending on whether you stay on the Right Bank or the Left Bank, the flat fees are 35 EU or 30 EU. The flat fees are good for 4 passengers and their luggage, and the 5th passenger will be charged an additional 4 EU.

You can book yourself by phone or online with this dependable company. You will pay a 7 EU reservation fee in addition to the flat fee:
https://www.g7.fr/en/book-taxi

We liked Hotel Excelsior Latin in the 5th, as well. Our three teen/adult kids shared one room with three beds, and we had our own room. No door between the rooms, just a wall, but it was air conditioned, pleasantly decorated, and the beds were really comfortable. We could walk easily to the sights we wanted, and Metro stops and RER station were convenient. On our last day, we walked to a bus stop to get to the train station for our TGV to Switzerland - easy to manage.

The hotel does offer breakfast, but we opted to go to Maison Pradier every morning! One nice perk of this hotel is a free coffee and hot cocoa machine for guests in the lobby. There was also an ice machine - which helped me out a LOT in the heat wave in 2015.

Check their website for photos of the arrangements for families of 5 - and then I'd recommend calling them to find the best fit and price for you.

Have fun!
Laurie

The Regina Hotel has family rooms and family suites. I believe that the family suite has a bunk bed and a single bed for the 3 children.

I would definitely rent an apartment - I've had great luck with Airbnb. I think that would be your best bet, especially if you want a kitchen and washer/dryer.

It's highly doubtful that someone could find enough beds for 5 people at this late date, even using AirBnB.
Probably a solo or a couple could find something, but not 5 people who want real beds.
It might be better to take a more realistic approach to finding lodging...