The LM317 will be sufficient. Add a 10 uF tantalum cap parallel to R8, a protection diode anti-parallel R7, another diode from LM317 terminal 2 -|>|- 3, make C3 a 0.1 uF ceramic, and make C4 a 1000 uF aluminum.
Couple that with good bypassing of the ADC's V+ (a 22 uF tant and a 2 nF ceramic in parallel, as close to V+ as possible) and you'll be fine.
Have you thought about feeding your thermistors with a larger voltage? Doesn't seem that you'll be getting the full benefit of your 12 bits/4.096 range.
I'd also add protect diodes to your MAX6241, pin 6 -|>|- 2 and 3 -|>|- 2.
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