The Lafayette City-Parish Council is slated Tuesday evening to discuss the idea of expanding the five-member Planning Commission.  The proposal is being submitted by Councilman Don Bertrand, who says the number of people on the commission isn't enough to reflect the amount of growth and development in Lafayette Parish.  Bertrand says the likely scenario is to add two members and perhaps two alternates to the panel.   The change would require an amendment to the home rule charter, which would need approval from voters.