For the cost and scope of your project I recommend MS Project. Personally I
dislike the software but many of your subcontractors will likely be using
it and the common platform will help all interact with little additional
If your project is not a run of the mill construction project I would use
Smartsheet and Basecamp. Combined these two platforms can have all the
power of Project and there is virtually no learning curve to start,
however there is a learning curve to extract their full power, especially
if a 20M project must land on time and within cost.
I do not know your level of expertise in PM but I am happy to talk more.
17+ Years in Enterprise Sales and Business Development in $700M+ of Investment Projects
December 20th, 2015
Oracle's Primavera P6 is the golden standard for project scheduling and tracking. Procore.com - great for documents exchange and tasks management.
If you can share more specifically what you are tryign to achieve, that could help you get better help here.