Yes, that's the idea. You need to ground pins 8 and 9 of the TC4467/8/9, and pin 10 isn't used.
Why did you choose such a high value for R4? I would use something like 12Ω or 22Ω to limit the peak current to about 0.5~1A to protect the TC4467/8/9 but still switch the MOSFET quickly.
Quick switching minimises power dissipation in the MOSFET, because it doesn't dissipate any power when it's OFF (no current flow through it), and it dissipates very little power when it's ON (low R
DSon means very little voltage drop across it); it only dissipates significant power during the change from OFF to ON and vice versa, so you want to minimise the duration of the change. This is more important when you're driving really big loads, but you have a good MOSFET driver there; you might as well use it!
You need decoupling capacitors on all of your ICs (and two on the regulator). It's best to draw them in now, so you don't forget them!
The IRF620 has a guaranteed ON-resistance (R
DSon) of 0.8Ω, at least ten times higher than most of the devices I recommended. This means it will dissipate much more power. In the worst case, 100% duty cycle with 2.5A drain current, its maximum power dissipation will be:
P = I
2 × R
= 2.5
2 × 0.8
= 5W.
A TO-220 package can dissipate around 0.5~1W without a heatsink. So you would need heatsinks if you use the IRF620. Not huge heatsinks; something with a thermal resistance of around 10 °C/W on each MOSFET would limit the rise to 50 °C above ambient. This will change somewhat if your panels draw less than 2.5A. The devices I suggested would not need heatsinking.
If you can't get the TC4467/8/9, try the Micrel MIC4467/8/9. There are a few other options as well. Who is your preferred supplier over there?
As for separating things out, that's a bit tricky, especially in an automotive environment. I think I would keep the MOSFETs with the controller if possible, with a cable to the LED panels, or put the controller in the LED panels along with the MOSFETs. Are either of those options feasible?
Re protection, I think this is what you should do. Keep the varistor at the +12V input to the circuit. Supply the LED panels directly from that rail. Include one power diode, e.g. 1N5404, reverse-connected across the series string of LEDs, to protect the LEDs themselves from negative voltages. Feed that rail through another 1N5404, in series this time, and a low-value fusible resistor e.g. 2.2Ω 2W (something like
http://www.digikey.com/product-detail/en/ERX-3SJ2R7A/P2.7W-3CT-ND/4079736 or
http://www.digikey.com/product-detail/en/FKN2WSJR-73-2R2/2.2DYCT-ND/2813222), to a 1000 µF/25V smoothing capacitor to 0V, and into the TC4467/8/9 power supply and the input of the 5V regulator. That should give you good protection.
I know 30W per bank is quite high. To be honest I am not sure if 30W will be necessary (it will likely be less, maybe 20W), but I have been using it as a starting point so that I don't end up under-designing it.
Good. That's my initial approach too.