Problem solved, thank you Iberia for your low fuel surcharges and better redemption rates than BA!
Outbound on 15 December, leaving Frankfurt via Madrid to Joburg (crazy routing I know!) But cannot complain for GBP391 per person return in economy...
On the return leg (26 December) I thought I'd upgrade them to make up for the weird routing. Got Joburg to Madrid Business Class tickets for EUR100 + 45,000 Avios each.
So total spend to get both my family members from Europe to South Africa and back for Christmas:
GBP782 + EUR200 + 90,000 Avios.
Much better than GBP1800 return in economy (for two) I was getting quoted on Skyscanner, and that was with Thomas Cook Airlines....