Sorry, long post!
We are still trying to find more info on that Executone WMA-35 amp. We believe it is probably made by Bogen but the closest I can find on the web is the WMA-80. This amp uses modules so it may not have a "line-in" module and it doesn't appear to have any bridge or line-out jacks.
The Peavey is on the web and it has those two RCA jacks which are just a summed input (meaning they are resistor wye adapted to mono inside) and no line out jacks.
If they were all Bogen TPU's, everything would be great, but we are dealing with a couple other brands here.
Bogen has the bridge jacks which as I mentioned before, is a two way link, almost like having a line-in and line-out travelling down the same cable. Bogen doesn't recommend it, but I have seen and done it where you take the bridge jack and feed it to a line in on another amp (like the Peavey). Without going into a lot of electronic detail here, it will be a test. It may work fine, or the line in circuitry may short out the bridge jacks causing no sound to carry over.
Here's your steps:
Basically pick a TPU100 and feed the tel page and your new "all call" mic into it (we'll call this our master). Use the mic input on this master for your new mic. It has two screw terminals for a low impedance mic and there is a ground terminal there too (XLR on mic, pins 2 & 3 will go to the screw terminals and pin 1, the shield, will go to ground). Make sure you use a low impedance, balanced mic for this (you mentioned you have to go about 100' for it).
Pick a second TPU and feed only the music into it (either use the RCA jack or the screw terminals), this will be our music zone amp. There are two screw terminals on this amp labelled "mute" and wire the switch from your new mic to these. This will mute the music on this zone when you are using the mic. Note how this is wired, the mic is actually wired to the master amp but the switch from it is wired to the music amp.
Take a RCA patch cord and plug it into one of the bridge jacks on the master. Cut the other plug off, strip the wires and feed them into either tel page or mic input. The bridge jack is actually a high impedance line level and since the music amp only has one high line level jack (the music jack which you are using) you will have to feed it into a lower level jack. The tel page being 600 ohms is probably your best bet but you will have to set that level a little higher on that amp. Do not plug it into the bridge jack on that amp otherwise you will carry the music back to the master which is not what you want.
Use a second RCA patch and from the other bridge jack on the master, patch it to the next TPU and so on with the remainder of the TPU's.
Test everything so far to make sure you have sound.
Now from the last TPU, patch the remaining bridge jack to one of those two music jacks on the Peavey. Test again to make sure this isn't shorting out the bridge jacks.
The Executone will somehow have to be fed as well, but without knowing what it has for inputs, I'm not sure what to tell you. It may be possible to use a wye adapter from that last TPU and feed it to both the Peavey and the Exec, but again, it will be a test.
If wiring it this way shorts out the bridging circuit, you will lose sound and have to make your own line out jacks. This can be done by wiring the following circuit: