In Canada, they suggest waiting until about 12 months old for cow's milk, but 11 months is pretty close.... You'd probably be fine with it, IMO, but that's up to you. If it's only 3 days a week, you could nurse the rest of the time, and try pumping while at work to give EBM? How easy would that be with your job?
At a year, we had about 4 breastfeeds (or equivalent - I was back at work) during the day (and kept that for ages - morning, bedtime, and after naps or for 2 snacks), plus we also had some nightfeeds for a while longer.
You could certainly start offering EBM or formula, and later cow's milk in a sippy.
HTH!