apartment or large hotel room in Le Marais

Have you checked Booking.com?
That will tell you if it’s even possible.
I doubt it in the Marais with the Olympics happening, but worth a few minutes to check and see.

I just randomly looked at 2 of my regular hotels in Paris around July 19. They are in the 7th, not the Marais. One has a triple for 527E/night, the other is completely booked from July 12 on. The 1st one is usually 275E or so per night and the 2nd is usually around 250E or less/night so you can see how the Olympics is inflating things. I'd check cancellation policies and if acceptable, book something while you continue to look.

The one with the triple in the 7th is Hotel Muguet.

https://hotelparismuguet.com/en/hotel.html

editing to add: I'd be pretty cautious about an apartment in the Olympic time frame. There are already several posts here and on Trip Advisor where people have had an apartment booked for months for this time frame and are getting cancelled out. I'm not an apartment person but I'd be pretty cautious and perhaps have a hotel back up if you can cancel close to the time.

That’s a tall order in the Marais at that price. I would look at hotels in the Astotel chain, namely Hotel George and Hotel Lorette ( although they have other properties). They offer apartments and family rooms with 3 beds in your budget. That area of the 9th is super charming. Lively, with lots of good restaurants and metro connections. It’s near the wonderful market street, Rue des Martyrs as well.

Indyhiker, i just walked rue des Martyrs today… : )

Try Hotel Turenne Le Marais on rue de Turenne. Rue de Turenne is a pretty busy street so noise could be an issue. It's not fancy but it is a clean and well run place and could be in budget.

Lucky you, Susan! My last visit was on a very rainy day in November. I hope to enjoy better weather on my next visit!

Yes, you are looking for a unicorn. Most hotel rooms in Paris are extremely small (120 sq ft). You might be able to find a full size bed and a twin, but 3 twins will be very difficult. I would start looking for two rooms: a twin room and a single room.

To find an apartment with three separate beds will be even more expensive. You would probably need one listed as a 3 br, since a living room with a sofa bed is considered a bedroom.

I've been looking for an apartment too (for two adults, two teens) and cobblestone paris had an excellent priced apartment in a good location for less than $300/night (with RS discount). Felt too good to be true!