If you're ok with offering formula, then once in a while without pumping is ok. At 2 months, your supply is still establishing so make sure to pump sometimes. For example, if you're going out to dinner and he gets a bottle, just pump when you get home. (you'll be engorged anyway) Try to keep to pumping when you would have fed. It is also pretty easy to pump with an ISIS in the car and put it in the fridge when you get home. LOL, I've done it!
If you can pump, of course that's better for him, especially at a young age. Some babies handle formula ok and some don't at all.