I personally find Indica's to do a better job at giving me the "munchies". I find when I smoke a more sativa dominant I end up getting so preoccupied with something (mostly my garden...or just my mind) that I forget about food all together. I would suggest something in the range of 3/4 Indica to start off.
In fact, there is a strain that was developed by the University of British Columbia specifically to treat chemotherapy patients. It is 80% Indica and 20% Sativa and goes by the name "UBC Chemo" or just simply "Chemo". Here is a short blurb from the website
http://www.drchronic.com/products.asp?recnumber=1154
"UBC Chemo
OUT OF STOCK DO NOT ORDER .................... Indoor / Outdoor Very strong with a hashy flavour, UBC Chemo was developed in the 1970's for cancer patients undergoing chemotherapy. Exhibiting characteristics of being a polyploid, woody stock and odd shaped leaves give the UBC Chemo a bonsai-like appearance. Recognized amongst the medical community as the best strain available for chronic pain and nausea. Flowering 9 weeks"
Generally speaking if a strain is said to help nausea and the likes then it will most likely work as an appetite stimulant as well.
The seed is offered through Federation Seeds, I hope this helps, my heart goes out to you and your family.


Edit. Got my Indica Sativa %s wrong. Correct is 20% Sativa and 80% Indica