I'd stay away from osmocote if this is an initial setup. The peat will have many of the trace nutrients the plants need. If you're planning on dosing the water column with ferts, this would be a unnecessary step with the exception of a few heavy root feeders. I'd say bypass the osmocote altogether. Osmocote leaves behind its little plastic shells even after the fertilizer is used up. I found this annoying as hell and a pain to clean up when uprooting plants.
"Can anyone tell me if the acidity of peat can convert the trace elements in it to a form accepted by plants?"
It can help a little until the bacteria get going, typically about a month or or so. But that assumes there are not enough traces are being dosed to the water column.......substrates can be used as a primary form/method of feertilization, but the water column will be the first places the plants will go for nutrients.
"Could you tell me what might be the dosage for this combination?"
No and I doubt anyone could really.
It's generally lesser amounts, I add roughly 1/4" in CO2 enriched tanks and 1" in non CO2 tanks(which reply more on the substrate for nutrients and cycling).
I add it to help keep the reducing power in good shape till the bacteria colonies form, this takes roughly a 3-6 weeks or so. The effects of the peat are worn off by then and the peat matter slowly decomposes.
As far as adding osmocote, I'd never suggest someone do this. Anything with NH4/urea is bad and should not be added to a substrate. I'd add soil before I'd add this or KNO3 and KH2PO4 and CMS etc.
Leonardite might interest you also.
Generally the pH ranges of 5-5.5 will optimize trace metals into their reduced forms. Around 100-200mv redox, Eh potential.
Keeping that layer seperated when you uproot and move things around will be tough as the layer will be affected by the water above which is a pH unit or two high and the redox is also 300-400mv higher.
You are not going to rev up plant growth significantly with all sorts of concotions in the substrate. If that is goal, you might consider adding more CO2, KNO3 etc. Or dosing more traces with chelators like DTPA etc to the water column.