Nice to see an employer trying to help out his workers
You could apply to extend their work permits but that will only buy them a little time. The only way for them to apply for PR is to get a job that is either under the low-skilled pilot program or a skilled job.
You can take a look at http://www5.hrsdc.gc.ca/NOC/English/NOC/2006/Occupations.aspx?val=7 and see if there are any skilled positions you could upgrade them to. Everything above "Major Group 74" on there are skilled jobs and everything below that are low skilled.
However, if you upgrade them to carpenters or something like that, you will have to pay them carpenters wages. You could look into if you can apprentice them, if you get an LMO for that and if that would be accepted by AINP.
You can also look at the AINP semi-skilled program to see if there are any NOCs there you might be able to put them under or if you have any contacts to try to get them jobs under an approved NOC. It's at http://www.alberta-canada.com/immigration/immigrate/semiskilledworkers.html