Outputting 10V from 7 ports, low current
Would something like an Arduino Mega be sufficient, with voltage doublers to get from 5V to 10V, to send those voltage outputs to our lighting unit


If you use a gain-of-two op-amp amplifier, you will probably need a supply voltage of 11 or 12 V for that circuit. With a 10 V supply, even if you choose a "rail-to-rail" output op-amp, you will probably not get an output above 9.9 V or so. Also watch out that the available current can get very limited as you try to get the op-amp output close to the rail. If your "low" current requirement is 1 uA, you'll be okay; if it's 10 mA, you'll probably need more supply headroom.

If 9.9 V is okay, then powering the amplifier circuit from a voltage-doubled 5 V could be made to work.

If a voltage doubler won't work, and you don't already have, say, a 12 V supply available, you can use a boost converter circuit to generate 12 or 15 V from your existing 5 V supply.


  I may also have to use something to convert the PWM signal closer to DC


All you need is a low-pass filter. A simple one can be implemented with just a resistor and capacitor (search for "RC filter"). If you want lower ripple than a single-pole filter gives you, you can likely combine a two-pole low-pass filter function with your 2x gain function in an op-amp circuit.