You almost got it right. Move the Start Trigger function from the AO line to the AI line. You don't need a start trigger on AO, set it to start immediately. Set the AI to start on digital edge. Then send the initiate command to the AI before the AO, just opposite to what you have. This way, the AI will be armed before the AO starts, and it will wait for the first rising edge to start reading. When the AO is started, the AI will start on first digital edge, and everything will be in sync.
Note that there will be a very slight propogation delay. The time it takes for the AO to get to the target, and for the target to return to the AI will be some finite time (picoseconds with small distances). This may or may not be of significance to you. If it is, there is another method to accurately sync the two. It involves exporting a sync signal to a pin out, wiring the pin to an AI incoming sync pin, and making sure the length of the sync signal travel is the same as the AO/AI signal travel. I can explain in detail if you need.