When my dog was in treatment for mast cell tumors, I researched what to do in case he lost his appetite. I actually never needed to practice what I researched because his appetite remained pretty steady throughout the course of the treatment. However, one of the things that I came across was something called NutriCal. It's supposed to be really appealing to dogs who won't eat due to illness or for other reasons. It is supposed to be high in calories and nutrients so that it can help increase energy, strength, stamina. I talked to my vet about it, and he agreed that it's a good dietary supplement. I think you can get it at certain pet stores, but you can also do a search on the internet and can buy online too.
Good luck. Freckles and your whole family are really inspirational. You really seem to all have such a wonderful, positive attitude. I know from working with human cancer patients that a positive outlook can do wonders in terms of the body's ability to heal and bounce back from illness. Keep up the good work!!