My suggestions are:

a) that you decide on the specific flooring you want installed.

b) that you decide on the inside doors you want installed.

c) that you ask Tim to specify the materials he needs to build the two sets of outside steps for the entrances. 

d) that the flooring be ordered and delivered from Shepley or from the mainland, before Tim arrives on the Island. Flooring which is received after Tim on the Island will not have time to adjust to the ambient humidity. Tim will not want either to wait around on the Island while the flooring is adjusting to the humidity, nor will he want to make two trips to the Island, one for receiving and a second trip for installing the flooring.  

e) as soon as Tim has started to install the flooring if not before, the inside doors should be ordered i) from Shepley or ii) from Home Depot via Cape Cod Express, to be delivered while Tim is installing the flooring. At the same time the material for the outside steps should be delivered.

f) as soon as Tim has started to install the flooring, (which at 200 sq ft per day will take him about 10 days) the Shepley representative be invited to estimate the wood requirements for the finish carpentry and to give a quote for the cost. You then have the opportunity to obtain the finish carpentry wood from the mainland via Cape Cod Express if it is much less expensive.