The best steps for getting a more accurate conversion from spot color to CMYK color space:
Save your spot color version, so that at some point you could potentially return to your two-color separations. Also make sure you save a version with editable text, since we'll need to update the venue/date info.
Then do a "Save As," saving out the version you're dong to be moving into CMYK color space. There is usually a closer fidelity to your spot colors if you first move the file into RGB color space. So go to:
Image > Mode > RGB color
Then, shift-select your two spot channels, and in the button to the top right of the channels window, select "Merge Spot Channels." This will redistribute your colors into the RGB color space.
Once that's accomplished go to:
Image > Mode > CMYK
This will move everything into CMYK color space -- a typical print format. here might be a bit of shift in the color tones, since CMYK color is limited in its saturations and values. But running it through the RGB color space tends to preserve more of the original color tones than merging directly from spot color mode to CMYK mode.