Will the JR Pass work for my itinerary?

I'm travelling with my sisters to Osaka on 3/1/19. We are all staying in Kyoto till 3/6. Will the JR Pass be useful sightseeing in Osaka & Kyoto? We are then going to Tokyo. However, while my sisters are proceeding to Tokyo Disney, I have to catch an 11 am flight at Narita Airport. Is there an early train from Kyoto to Tokyo or should I leave on 3/5 to catch my flight? Is there a reliable overnight bus?
I will greatly appreciate any advise. Thank you very much!

Yes, there is an overnight bus. https://www.keihanbus.jp/highway/line/kyoto-choshi/

Another option would be to take an early flight from ITM. Both ANA and JAL have flights leaving around 8 arriving around 9, which should be fine for your departing flight at 11. Take the ANA (resp., JAL) flight if your international flight departs from Terminal 1 (resp., 2) so you don't have to change terminals. There are also LCC flights from KIX, but then the transfer at NRT would be more challenging.

I am truly grateful for the quick response! It is very helpful.

About JR Pass: if the only long-distance travel you are doing is Kyoto to Tokyo one-way (and even this might be replaced by an overnight bus), then getting a nationwide JR Pass will not pay off.

Note that gJR Passh is only valid on JR = Japan Rail trains, and where it really makes a difference is when you travel a lot on JR Shinkansen trains. For a 7-day JR Pass to pay off, youfd have to make at least a round trip on JR Shinkansen trains within a 7-day period. So even for your sisters it will not pay off.

If you take the earliest train (Shinkansen Nozomi #200) from Kyoto which departs at 06:14, and after two transfers through rush hour Tokyo and Nippori stations to get on the Skyliner #17, you can arrive in Narita at 09:35. You will have to decide whether that's adequate for your flight. That's the best you can do if you decide to take trains in the morning.

While this transfer that the PP describes might be possible you have two transfers at busy stations you donft know and the skylines is a reserved seat only train. I believe you can buy that ticket upfront on the internet, otherwise you need to factor in time to get the ticket at Nippori.
So you should probably count on arriving at Narita only 20 min later, to be on the safe side on transfers and ticket. It would sound like quite some unnecessary stress in the early morning when you could easily take the train in the evening and get a hotel for your last night in Narita.

We all assume that your ticket is already booked and you canft change it to leave from Osaka (KIX) instead. Might be worth checking though.

And yes, as PP said the 7 day pass will not payoff for any of you.

Enjoy your trip to Japan!