You can keep nursing when you're together, and don't necessarily have to provide ebm or any other milk when you're apart, depending on how often you DC is still nursing when you're together.
I went back to work when DD was 10 mos, and she stayed at home with DH for another 2 mos. I did pump for her for a while, but she decided after about 4 weeks that she was totally disinterested in ebm. She's done fine ever since on H20 and diluted juices. We've never bothered with other milks, as she continued to nurse like crazy when we were together and thru the night.
I'm not a big fan of weaning in preparation for separation - that just seems like a lot of unnecessary stress for both of you if you ask me. I agree with the poster who said that no bf was just part of mommy not being there.
If you have onsite care - wtg! But keep in mind that it may be difficult for your child to have you come and go, especially if you cannot commit to having a regular time every day. Even at 2.75 yrs, my DD freaks out if she sees me at the dc during the middle of the day - she assumes that I'm there to take her home. She loves it there, but its too confusing for her when I leave without her.
If you do end up not nursing or pumping during your work day long term, you will still need to give your body a period of adjustment, IE weaning yourself off producing milk during those hours. To start with, you should reduce either the time or volume of pumping/expression very little (eg 1 or 2 minutes less, or 1 oz less) at each session for a few days, then reduce it again, then start stretching out the period between sessions. Trust me - you don't want to end up with plugged ducts or mastitis when you've just returned to work!
That said, especially since your child is nearing the 12 mos mark, your supply is well enough established to be able to handle nursing on cue when you're together and not nursing when you're apart. You might feel a bit full on Monday evening, and your DC might have to work for it on Friday night, but it is amazing how your body can respond to DC's needs!