[Findegil]

As said before, JRR Toklien change the idea of second-live of the Elves. He came in the end to the conclusion that the Elves were not reborn as children, because they were supposed to continue their former live.
The Elves were re-incarnated, that means the fea (soul) was put into a new-build hoar (body). The new hoar was an exact copy of the one that perished and it was fabricated by the Valar. So the re-incarneted Elves were in Valinor and almost all stayed their. Some Elves did not desire re-incarnation and to some it was denied by Mandos.

It is right that JRR Tolkien hesitated also about the rebirth of the Fathers of the Dwarves. But there is no evidence that he rejected it entirely for them.
In view of the topic I put out the theory that the gift for the Dwarves was real rebirth as children. This is of course only a theory, back-uped only by the Fathers of the Dwarves who gained full memory of thier former lives. But Gimli showed also some hints of "racial-memory". He tells the fellowship that they, the Dwarves of Erebor, dream about the three pikes of Moria, and he recognised the Balrog for what it was called by the Dwarves, "Durin's Bane".

To put it straight my theory is:
All Dwarves were reborn as children in their own kin. Only the Fathers of the Dwarves came, when they had grown up, to full memory of thier former lives. All other Dwarves had only faint memory as revaled in dreams and visions.

Respectfully
Findegil