QuestionS!!
1) NEW job?? Hooray--are you happy?!
2...) Why 2 RT's? Why not ATL/LAS/MIA/ATL with stopover in MIA? Isn't that a legal booking on buddy pass?

If you have 2 sep YF tkts you have to ck in somewhere, that's for sure but I don't believe LAS can ck you in for ATL/MIA if sep yield fare tkt.
Now, if they are one tkt, LAS can ck you in a through pax. That's how I understand it--definitely need to see if trip can be combined as one tkt. They still have red phones in ATL so you can do Delta Direct there--so you shouldn't need to exit security to ck in at kiosk. When do you depart? Ck w/ck-in agent ATL about combining tkt before you leave fro LAS.

Let us know what works or doesn't, ok?