He probably only needs 3 ounces for 2 hours, you're supposed to give 1-1.5oz for every hour apart. So one more pump tomorrow and you'd have enough if you feed before you go and as soon as you're back! He'll probably naturally drink less when apart from you. It's really not that long, he won't starve I promise, your mum will probably find another way to settle him if he's upset. It seems much scarier than it is but babies are so adaptable. X
So my daughter is EBF too and feeds roughly every 2-3 hours through the day and not at all at night. She won't take a bottle (started refusing around 6 weeks and hasn't had once since). So when I go anywhere I just make sure she's had an extra big feed immediately before I leave and I find she can last the 3 hours absolutely fine. X
Ebf can usually go without a feed for 3 hours. If you're feeling him before getting will most likely be OK till you get back. But if he needs a top up your mum can give him the amount you expressed, it doesn't need to be in a bottle she can give it in a cup and slowly let him feed. I was unwell after labour and the midwife gave my LO milk in a cup and said its better as they don't need to work for it. Don't worry your LO should be fine. Plus the only need 4oz of expressed milk on a feed, you've nearly expressed half.
I had kit days at work and planned on pumping before hand but she feeds so frequently it just didn't work out. So my husband used ready made formula. I do 12 hour shifts so I can pump at work otherwise I'm ready to explode, freeze and use for next time. But 2 hours isn't long, he won't need much whilst you're gone just give a good feed before you leave. X
I’ve had friends who have had KIT days at work and had to express ahead of time or use bottle milk. Ultimately, if the baby is hungry they will feed. If they can sense you aren’t there too, they will drink if hungry x