Quick and dirty plan: goal here is to make sure we don't get hit as hard by the colonists by improving sanitation (reducing the chance at nasty diseases, because, well, colonists), as well as econ improvements and, via calendar and rituals, the methods and tools needed to do ritual strikes against the colonists if they decide to pull a...well, colonizer.
IC non-Metagaming;
-The colonists have thus far been nothing less than friendly to the True People they encountered
-They have some really impressive material science that would be very nice to acquire via trade
-They're different from us, but that doesn't mean we should fear them or assume they're a threat
-Particularly when we have real threats in the form of the League of Strength, the Tech Barons, and the Machine Army.
-These are the threats we should focus on preparing for, and the colonists could be powerful allies
OOC Metagaming
-We are not Native Americans
-The colonists are not Europeans
-This is an independent group of religious/political refugees. There's unlikely to be continuous waves of additional colonists all seeking land.
-They're also unlikely to be terribly focused on exploiting our resources for export because they have nowhere to export to.
-There are possible sources of conflict (they'll need resources for their own use and I doubt they share our views on land ownership) but conflict is neither inevitable nor desirable
-The colonists have good material science. We need material science.
-We also have powerful enemies all over the place and don't need more.
However you slice it we should reach out to the colonists and see if cooperation and trade are possible, whilst focusing our military preparations for more immediate threats.