1st day arrival in Paris and Itinerary

Where are you arriving from and where are you staying in Paris? Suggestions for what to do on your first day will depend on whether you will be jetlagged and where you are. Usually, suggestions are to drop luggage at your hotel, get some breakfast or lunch, and walk. If coming in from an intercontinental flight, avoid museums and bus/boat trips that will lull you to sleep. Generally, explore your neighborhood, walk down to the river, staying outside until you can check in to your lodging. After dinner, try to stay up in til 9:00 or so before going to bed. It usually takes me 2 or 3 nights to start sleeping normally.

Flying from US to CDG airport. Staying in the Latin Quarter

What would be the best day to take a day trip to Versailles and then a day trip to Disneyland?

I laughed when I read your post, because it's exactly like our upcoming stay, including Versailles and DLP.

Since you're there in summer, try to plan DLP for a weekday to minimize crowds and lines. Give yourself plenty of time for the train ride to Marne La Vallee-Chessy so that you arrive well before the park gates open. Buy your park tickets in advance, if possible. And be sure you know when the last train of the night leaves!

Are you coming in from CDG? Even though you likely won't be able to check in, go to your hotel and have them store your bags for you. Then head out to explore. If you're like me, I'm half zombie due to jet lag on arrival day. Walking and fresh air really helps. Ricks suggested historic walk that starts at Note Dame is something that we often do. We'll grab lunch at a cafe on the Left Bank during the walk. Return to your hotel at check in time and freshen up/unpack. The front desk is usually happy to give you some restaurant suggestions near your hotel for dinner. Then turn in early, maybe after a stroll along the Seine to see ND lit up at night. You'll have earned a good sleep.

You don't say where you will be coming from, so I don't know what your jetlag situation will be, or what your interests are, so I will make suggestions of what I would do.
First, I would recommend taking a taxi to your apartment or hotel, even if you will be using the Metro extensively later. Trying to use the Metro with your luggage when you are tired/jetlagged is awful. It is worth the $50 for a taxi. Once you drop off your bags, I would head out to walk and just enjoy your first sights of this wonderful city. Generally, the best way to help yourself acclimate is to be in the sunshine, so I would plan the first day accordingly. Perhaps walk along the Seine, stopping for lunch at a street-side brasserie. One place we love is Petit Pointoise, situated right next to the Seine, in the heart of the Latin Quarter. They are open for lunch and dinner 7 days a week, and reservations are recommended, which you can make online. (Their escargot is on my list of 5 all-time favorite dishes, ever. It's very different from other escargot -- please try it!) Then head toward Notre Dame, taking time to go inside if the line is not too long. Continue on down the river toward the west, toward the Tuillerie Garden, which has lovely shade trees and chairs perfect for a rest. To get a great view of the city, go to the top of the Montparnasse Tower. Tickets are inexpensive, and the view is as magnificent as it is from the top of the Eiffel Tower, without having to get ET tickets and endure the crowds on the elevator there. If you are exhausted and failing, there is no shame in returning to your hotel to nap for half an hour or so, freshen up, then head out again. Another good first day activity which lets you rest while being in the sun is to take a Seine river cruise. No need to reserve ahead -- just get on one and go. (I would avoid Bateau Mouches at all costs, as it caters to the big tour buses. Trust me on this -- I learned the hard way.) I would finish out the day by going to the Eiffel Tower around 9:00 to grab crepes for dinner at the base and then to see the sparkle at the top of the hour.
On subsequent days, plan around the sights you want to see. Assuming you wish to visit both the D'Orsay and Louvre, I would plan to be at both of those first thing in the morning -- be inline about 15 minutes before they open. Alternately, both have evenings when they are open late, and going later in the day when other tourists are tiring and leaving can work well. One of my favorite museum experiences in Paris is to arrive early at the D'Orsay and immediately head up to the top floor to the impressionist area. Being alone, or almost alone in those galleries, is indescribably so much nicer than having to jockey for a good position when the crowd arrives. (You know, I am sure, that you have to use your museum pass on consecutive days, so plan accordingly.) Other sites we really like are the Rodin, the Orangerie, the Opera Garnier, and Saint Chappel. But the best part of Paris is wandering and exploring, sitting in cafes and enjoying just being there. We really like to sit out on the Plaza in front of Notre Dame in the evenings to people watch. Have fun!

Thursday
•Arrive early
•Walk off some jet lag in the Luxembourg Gardens
•Purchase your 4 day Paris Museum Pass and visit either the Cluny Museum or Panthéon
•Musee d'Orsay
(Closes late Thu at 9.45pm)

Friday
•Sainte-Chapelle (Opens 9am)
•Arc de Triomphe (Opens 10am)
•Tuileries Gardens (Orangerie)
•Louvre Museum
(Closes late Wed,Fri at 9.45pm)

Saturday
•Notre-Dame de Paris (Towers open 10am)
•Picasso Museum
•Place des Vosges
•Centre Pompidou
(Closes late at 10pm - ex Tue)

Sunday
•Versailles

Monday
•Eiffel Tower (Opens 9:30am)
•Sacré-Coeur & Montmartre
•Evening Seine Cruise

Tuesday
•Disneyland

Since you're getting the museum pass, set your schedule so that you visit the sites covered by it on consecutive days...i.e., 4-day pass use on 4 consecutive days. I'd personally skip Disney in favor of something like Fountainblue, Giverny or Chartre......but to each their own.

Because most museums tend to close on Monday or Tuesday, I would suggest the 4 day Museum Pass for Thu-Sun. Visit other sights, like Disneyland. Montmartre, Eiffel Tower, on Mon-Tue.

It will likely be blazing hot the first week in August.
If you are renting an apartment without air-conditioning, you will need some fans - which you might have to buy yourself. Close shutters, windows and drapes during the day and open during the very early morning and late at night.

If you're staying in an air-conditioned hotel, you'll be relatively comfortable.

There is virtually no air-conditioning in museums, restaurants, department stores,

major monuments, and the Metro and Bus system - so I would not go at top speed to do the things you intend to do.
Drink water instead of alcohol, and eat light meals - even If you are tempted, you might regret it. Stay in the shade, wear light-colored clothing and straw hats.

If going on a bike tour to Versailles, be sure that everybody can handle the heat.
The same goes for DLP.

I think Rick's "Historic Paris Walk" is a great introduction to the city, as well as a good way to stay outdoors to fight jet lag. You can get his free audioguide for it on his app, or on this website (scroll down to the bottom): https://www.ricksteves.com/watch-read-listen/audio/audio-tours/paris

In addition to Chexbre's beat the heat tips - get one of those folding fabric or paper fans at a souvenir stand/store. I remember one August trip in Paris where it was hitting 40 C. daily. We were lucky that our hotel had AC, but being out and about was brutal. That souvenir fan came in mighty handy to create a little man made breeze. I got the idea while riding on a stifling metro and seeing several ladies using them. And it tucks away easily in your bag when not using it.