MIDI to CV circuit design

So, I am led to believe that this circuit should do the trick. I am going to lay it out on veroboard so there is enough room for tweaks in case I need to do something more to smooth the Control Voltage, but if I'm honest, I am not going to know until I start playing with the ICL8083 (waveform generator chip). At this stage I feel that its best that I get this end built up. The fine calibration is going to have to happen afterwards, when I have the 8083 to play with, because I really need to 'listen' to the results to see if they are good enough.

At the moment I'm finding progression hard because I do not have a stable platform. After I have the 3 core modules (CV, Waveform, Mixer/amp) sorted, the subsequent modules will be open to a lot more prototyping.

Description: U2 is the Arduino Chip that will need to be bootloaded and programmed up with my desired software (more discussion on this later). U7 is the opto-isolator that is required for the 'Midi In' stage. U1 is the DAC (that apparently doesn't like being de-coupled). U3 is the reference generator (the application notes in the data sheeet don't ever mention decoupling caps, but I will leave space for this on the board just in case). U8 is an op amp, I'm not sure how essential this is, but because I do not know exactly what we will be doing with the CV afterwards I thought this was a good idea to stabilise the system, hopefully I won't accidental put too much strain on the DAC. J6 J7 and R9 are the extras that will allow the right information into the arduino to create the static voltages and the sweep. J4 will we software controlled and provide a "Gate" output, 0V to +5V. This will be used later by the VCF.
This is the power and bus requirements of the circuit, R2 and R3 provide us with a split +12v and -12v power to play with, but because this circuit does not require -12v have have not included the -12v VREG. The Arduino however requires regulated +5v so I have provided one. The reason I have opted for the top end out the +24v to be used is because In the next module, the waveform generator, I would like to give the chip +/-12v, the common ground will be 0V. because all these modules will be linked I wanted the Common ground between the modules to be the same. Making 0v on the PSU -12v below the gorund for these circuits. (kinda making my +12 and +5 on my PSU bus redundant, but... Que Sera...)