How much ebm to give?

[ipswichwitch]

DS1 is going into hospital tomorrow and DS2 (5mo) will be looked after by ILs from 10-8ish. DS2 is ebf but will obviously be bottle fed expressed milk tomorrow.
My question is, how much milk will I need to provide? He's feeding every 2-2.5 hours, and has taken a bottle a few times before, but only about 3oz each time. I have stacks of milk in the freezer but I have no idea how much to get out. SIL will have him for a few hours at hers then MIL will bring him home and look after him til I get back.
Does anyone have any idea how much milk he's likely to need?

Can you just give them a stash of frozen milk which they can defrost as needed and then take back what was not needed?

On average breastfed babies take about 25oz a day, so if he's having 8ish feeds then 3oz per feed is probably right.

Ok thanks. McBaby I could send over extra kept frozen - don't know why I never thought of it!
TheScience, I never knew how many oz a bf baby usually has a day, so thanks for that. I can work out how many bags I need plus keep a few extra frozen in case he's greedy. It's hard to know how much he has I guess because he's bf so there's no way to measure!!