During winter, children are especially susceptible to coughs and colds, so this year we decided to make our own immune boosting cough syrup to keep bugs at bay and speed up our recovery time. For this particular recipe, I included the herb Astragalus (also known as Huang Qi), which is commonly available from Chinese herbal shops, but may be difficult to source otherwise.
Typically honey does lose its beneficial properties during processing (involves heating), which is why it's best to buy raw organic honey where possible. The consensus though is that Manuka honey is far more chemically stable and better able to retain its anti-bacterial properties when heated.
Perhaps add the honey at the end of this process and heat very gently until it's combined with the rest of the syrup. It's still preferable to sugar!
I agree that the recipe includes a fair bit of sugar - you could replace it with honey, but you would need a LOT to make it thick enough. If you are making this for kids - you will need a fair bit of sweetener, but you could reduce it significantly for adults.