Cindy,
I've done some giclee prints on canvas of oils that I've painted. In the past, I've done off-set lithos on paper and also photo reproductions. I like the giclee on canvas so much better, and welcome this newer technology. I think for a portrait, giclees on canvas are an excellent answer for customers wanting copies for grandparents etc.
I stretch the canvas prints and frame them the same as oils and they look great. However, I make the prints slightly smaller then the original. The quality of the prints are so good, that I think it is important to keep something special about the original and for me size is the answer. An inch smaller all around reduces it enough to maintain the specialness of the original. Several inches smaller can make an "intimate reproduction" that is also worth considering.
I agree with the others that there should be a mark up. You can always come up with a couple different size and price possibilites. There doesn't have to be a big markup, but your time in getting them made is worth something plus some profit. The customer has the option not to order the prints if they aren't happy with the prices.
The company that I used has a set price for a sheet size of 35"x47". The price per print depends on how many prints you can fit on the sheet. Naturally, the smaller the print, the more prints per sheet. Their website is
http://www.oldtowneditions.com/. In addition to being pleased with their quality, I found them very easy to work with.
Mary