Kia Ora, Pelion, Lees Paddocks, out is a long day, maybe 9 hrs
2 alternatives to shorten the trip
moses ck track to Junction lake rather than lakes Myrtle and Meston, 5-6 hrs
pad from the OT just S of Kia Ora hut to lees paddocks and the RD 6 hrs
Using these tracks I had a gorgeous circuit last June crisp frosty sunny weather, 3 days.
viewtopic.php?f=42&t=13914 These tracks take a bit more nav than the route you describe.
details of the tracks on this website
http://tastracks.webs.com/merseyvalley.htm also in John Chapmans book on the OT and WOJ
If you had 4 or 5 days you could explore the waterfalls maybe climb a peak or 2
All the best for your trip