Your suggestions helped me find the issue - thank you soo much for your assistance! I'd like to share the cause and fix so if anyone else has this issue they can find it. I looked in LOOT and saw the following error:
-FacegenForKids.esp: An unresolved reference to a package from an older version of USSEP, must be removed from record 00014132 in FacegenForKids.esp. Guide: https://macsplody.github.io/xGuides/#-simple-children-
I also saw this error in my SKSE log: Unhandled exception "EXCEPTION_ACCESS_VIOLATION" at 0x7FF7DF506370 SkyrimSE.exe+0196370. A google search told me that others had seen that error related to facegen problems.
I disabled the FacegenForKids ESP plugin in the Simple Children mod, re-launched, and the menu loaded! Completing the instructions in the link permanently fixed the problem - I can now launch the game with no issues, and I was able to finish the performance benchmark section
Now I'm on step 5, LOD generation, and Dyndolod keeps giving me a BSOD - it did finally finish, but I suspect there are a bunch of missing textures because I have purple squares all over the place I'm assuming this is because Dyndolod kept crashing. I'm currently updating all my drivers and the BIOS. If that doesn't resolve the BSOD, should I start a new post in this forum or the Dyndolod forum? Brand new to STEP so I'm still learning the rules.