I'm glad to hear it's just a mild flu. The'll be ok in no time
I've learned a trick in the shelter I used to work in, to give scared kitties their medicine. You lay a blanket or large towel on a table, or on you bed for example.
Pick the cat up and put it in the middle of the blanket with more fabric to the back and just about 20 cm fabric to the front. Hold the cat there with one hand. Fold a strip of blanket over the front paws, then fold the sides over the cat, so they're reall tight and the paws are snug in the fabric strip. Then fold over the back piece of fabric, so you have the cat in a tight bundle. You can now give them their medicine. Do it careful though!
All the best for your kitties!!