We had the same thing happen to our pup only about a month ago - and it is sooooo scary!!!!!!! Lucky for us she didn't go into shock but within 5 mins of the sting (which was on her bottom lip) her face had swollen so much her eyes were shut, she was vomiting everywhere, and had lumps and bumps all over her....our specialist said she is allergic and too get somesort of injection pen similar to what diabetics have and carry that with you with adrenalin, you will need to get a script though from your vet!!!
As for your capeweed problem not to sure about that one, we have been trying to do the same thing in our backyard, gettting rid of all the flowering things that attract bees. I actually think that capeweed (if thats the clover type weed) has to be dug out, as sprays will not kill it ......GOOD LUCK