Hi Lynwen
Welcome to Australia

, but I have found very little information for you.
I have a copy of the AVRI which covers early Oz BDMs for NSW TAS VIC and WA. I can only find 3 references to the name Mallindine. It is a tricky CD to check for variations in spelling, but I looked for some close variations with no success
Male Mallindine born 2 May 1850 Father Henry Mother Martha Martin Reg 1851 ref 421
Henry Mallindine age 0 died 11 Aug 1851 reg 1851 ref 870
Henry Mallindine aged 54 married Jane Mold age 67 28 Apr 1877 ref 269
It would seem the young male may have died, my data gives 1850 as his birth & 1851 as the death (although age 0 in 1851 could indicate a birth year of 1851).
Despite civil registration starting in 1838 in Tasmania there do seem to be missing records
Trish