So, I finally got my tickets sorted. Rather than a long post with all the gory details, if you are interested, the novella in installments is posted in the comments section on the pointhacks page (my handle there is kmc).
Don't miss: Malaysia Airlines offering 50% (!) discount on Enrich redemptions until 8th December - Point Hacks
The executive summary is that it wasn't easy, and I was on hold for a long time. I think I am now in possession of tickets for 2 adults, 1 child and 1 infant BNE-KUL (1 day stop-over) KUL-LHR (3 week holiday) CDG-KUL (1 day stop-over) KUL-BNE. Taxes and infant ticket cost for all sectors and all passengers approx $4000 and 285000 MR points total. Given that paid tickets can be had for ~$16000, I guess it was worth it, but it did take a long time to finalise.
Seat selection? I'll do that another night!