VAG, depends how purist you are ;) It depends how you look at it, is he already on solids, I can?t remember? If so, all the major benefits of BF are in the past, his virgin gut is no longer virgin anymore, so a weekend without BF is neither here nor there.
Obv to some who think formula is the devil then of course you are liable to poison baybee just by having him took at the tin. But in the real world populated by actual people then give it, especially if you find expressing hard (But if it?s just a 24 hour trip, then you?ll only need to leave around 25oz, so getting 4 oz per expression sesh means not that long till you?ve got enough).
Seriously of course if we are being honest there are health benefits to the baby to be ebf for the first 6m, it?s why it?s the recommended feeding method, but it?s not like we have the dangers of ffing in a country with no safe drinking water and all that jazz is it? I
Some babies won?t drink formula if they?re used to BM though, so if you do decide to do that, try it before you go to make sure, you don?t want to starve him!