Analog and digital ground plan with isolated DC-DC converter
It is a good idea to use separate ground planes for AGND and GND. As you mentioned, they must be (in most cases) connected only in a single point, ideally using a ferrite bead or another kind of small inductor, so DC levels are equal but high frequency noise, coming from the digital part, is blocked from entering the analog part.
All analog parts must be near to each other, and away from digital parts, which must also be grouped together. It is good to have short paths to the supplies and use decoupling capacitors.
Isolation helps to reduce conducted noise, but it may not be necessary if noise is not too bad. Remember that isolation is from the the 24 V supply, but in any case AGND and GND must be connected at one point. Since you want negative voltages for the opamps is likely that you will have to use isolation. If you do not want isolation you could change your circuit to use single supply opamps.
For more information on how to do the a split plane grounding you can check this application note or just google something like &quot;mixed signal grounding techniques&quot;.