If you can pump enough to feed him (I can't, and I've bf three kids) and he doesn't take the bottle you still may have to try and feed him. My advice is this: either wear a vest top and a normal top so you can pull the vest down with your bra and the other top up, or a proper bf top. Sorry if I'm talking like you're stupid, but when I first started bf in public I was worried about exposing myself, and my dc never like the muslin either.
If you have a mirror you can feed in front of, have a go, you'll be surprised how little boob others see. Also, a baby quietly feeding at his age people often think you're just cuddling him.
Long term if you want to feed in public, and I did I believe you need to get practise it. I took mum to a Costa and we sat and I fed dd there while she distracted me from feeling self conscious. This was six years ago now and it must have worked, because I've fed three dc in all manner of places.
Please go easy on yourself, I totally remember being really nervous for quite some time about this, the phrase fake it till you make it springs to mind, it will get easier and you will feel more comfortable, at least I did anyway. And you never know, in situations like this, especially if my dc were in a sling, they'd sometimes have a power nap and sleep the whole way there and back!
Wow, didn't meant to write an essay, hope I've helped at least a little. 