According to the NRL website a decision on which days both Finals will be played will be made after week 2.
Week Three: Preliminary Finals
The highest qualifying teams (after re-ranking following week 1 results) in each match (winners 1 & 2) will host in their home Region.
The following Regions and venues may qualify to host a Final in Week 3:
New South Wales/ACT:
All Teams: Sydney Football Stadium, ANZ Stadium
Queensland:
South East Queensland Region: Suncorp Stadium
North Queensland Region: Dairy Farmers Stadium
Victoria:
Melbourne: Etihad Stadium, MCG
* A decision on which days both Finals will be played will be made following the completion of Week 2