The second Joel Rosenberg Novel "The Sword and the Chain" talks about a small group of folks moving to an isolated valley to set up a new village; I find it applicable as the settlers did not plan on coming back to regular society for some time. I'll summarize what they felt were necessary and how they went about constructing the settlement.
First off is the location. Not only does it have to be accessible by whatever means of transportation will bring more colonists and supplies BUT it has to have some type of potable water source. Streams and/or rivers are preferable as their energy can be harnessed by a mill and used to transport materials.
Second is defense, primarily from natural predators. And while bears are not likely to eat the settlers, they MAY raid their food supply and leave the group short on edibles, etc. Plus, a good wall (of whatever building material is in abundant supply) can also be used as one wall for dwellings and other buildings built against it.
Wood is such a predominate building material for a couple of reasons. One, it is very versatile relatively easy to work with. Two, often acres of trees had to be cleared to make enough room for the settlement - why not find ways to build with the material? However, wood is not essential except for a few key processes. Mud, clay, stone, straw, etc. can be used to build both the walls and the dwellings. However, remember that fire is also a necessary item and fuel is key.
One building that will need to be built quickly is the smithy. Nails, horseshoes, etc. are going to be needed pretty early on. Having someone on hand who can make simple weapons (arrowheads, short swords, daggers, etc.) will also be of help.
Obviously, a large daily task will be food gathering. Some will be brought on the trip, but the dietary needs of a settlement are big and immediate augmentation would be required. Another structure that will have to be built early will be the animal pens. There will have to be some protein source, and while much of what is hunted will be killed and eaten right away, the notion of a settlement essentially demands keeping and breeding animals of some kind: chicken, cows, etc. Of course select animals with dual natures: chickens both lay eggs and serve as food. Oxen can pull plows and move goods while they breed with the cows that give milk. Successful settlements have to be keenly efficient as there is just not surplus ANYTHING: space, time, etc.
Tell me how the campaign goes, as this is an interesting idea!