AFAIK the relevant reactions are something like this:
[FeEDTA]- + Ag + Br- <===> [FeEDTA]-- + AgBr
The NH
4+ counter cation to the Ferric/Ferrous EDTA complex maintains high solubility of the salt, and with its mild solvent action somewhat accelerates bleaching. At the pH most Ferric EDTA bleaches operate, we can assume that the NH
4+ counter cation is mostly dissociated.
T.H. James states the restoration equation roughly as this (Theory of the Photographic Process, 4
th edition, page 451):
2 [FeEDTA]-- + 1/2 O2 + H2O <===> 2 [FeEDTA]- + 2 OH-
which is essentially what you suggested.
If you consider, that typical Ferric EDTA bleaches use lots and lots of Ferric EDTA compared to the amount of silver which is bleached, and given that EDTA is a fairly good buffer at typical bleach pH, I would not expect a large change in pH unless you use this bleach until the bitter end.