Well this makes things tough. SInce you can't do the LHR-DXB MR (given that you MUST be in ATH to visit family), you will have to make up the SCs in NA and Asia.

In Europe pick a city which is more than 1000 miles from LHR - round trip (instead of LHR-DXB-LHR) will net 120 SCs.

In NA add some sectors, and voila:

syd-jfk-phx-jfk-lax-mia-ord-lax-lhr-ath-lhr-ist-lhr-nrt-hkg-nrt-mel-syd

Total miles = 48768
Total SCs = 1450

If you already have some SCs this year I would omit one or more of the NA sectors (as that's a lot of flying in very little time in NA)