Definitely two kittens!!!!!!!!!!!!!! Let the babies entertain each other, distract each other and pester each other... let sweet Yoda enoy watching them, without any demands on her by a single kitten to be the playmate. She will join in when and if she desires, and she will sit back and watch if she prefers. This way, she can choose her level of involvement. I don't believe that two kittens will somehow prevent bonding or sisterhood on the part of Yoda!!! I don't think she can exactly ignore their presence, or anything like that!
I don't think you need to anticipate a difficult integration. Expect the best, trust your animals and your household stability, set the tone for calm success.... and provide those babies with a space to be babies and let Yoda choose how it goes. I doubt she will attack them. Maybe you can put them in a room with a divider that Yoda can cross and the kittens cannot cross (if this is possible)... and let them adjust to a new home and let Yoda adjust to them... if it is too stressful that way, you can create larger/ stronger boundaries.
I have rescued and fostered, so my own cats have had to deal with new animals coming through the home regularly. I expect them to just deal with it; we have a higher cause we are dealing with, and I don't really entertain the possibility of them being rude about it, and... to be honest... it has changed all of us for the better. My extremely aggressive male is now "Grandpa" to a tiny kitten who helped him find his inner paternal side... etc etc. and has found some tolerance and acceptance of the crazy ways of the world.
I am sorry for your loss of Jedi's presence in your home... I wish you peace, especially in the face of a sudden illness in a young cat.