What can an employer do to put his expatriate employees at ease in the host country {Nigeria)?

Should the organization set assignment lengths of one year or two with families? What does research say is the optimal time period?
If there are families, what would be the children’s school arrangements?
How will the employees be housed?
Do they need an increased housing allowance, or does the organization need to procure its own compound of apartment housing?

it is important to notice that the expatriates employees are in Nigeria for an agriculture project.