This is tricky because supply comes from demand. I realize you don't want to be tied to the pump, but this high output may not last over time. My sister threw out milk vs freezing it and had to supplement with formula by the time her son was 7 mo. You should read kellymom.com - there is exclusive pumper information in there. You might also consider pumping one side while he nurses from the other and 1. save time and 2. get the benefit of his nursing to activate letdown. Remember that this is temporary and will likely peak at 6 mo. and taper down after that.
Other suggestions only because I was so nervous about nursing in public. If you ever find yourself out and about with no bottle and still nurse him sometimes, then you can find a changing room to sit in. I was really nervous about nursing DD in public when she was born and at first I would find a mother's room or a changing room. I got caught short at a work gig (of course) and had to pull out my cover and pretend I didn't care what the guy from Engineering thought. So if you get caught short, don't panic. Just find somewhere private to sit if you don't want to sit out in the open.
And make sure you have the right "horns" or whatever they are called. I had to go up a size, and they now make more flexible/comfortable ones. It can help you output, especially if you later pump longer but less frequently. And also make sure the suction is right. You don't need to rip your nipples off to get milk. Ouch.