Do you mean post-op liquid diet? Slimfast are good, so are the other stuff you listed.
If you like chocolate, Options are a good choice, as you can make with milk. Ovaltine is good.
Don't forget Oxo / Bovril / bit-less soups - packet / tinned.
I lived for 4 weeks on this combination; make sure you have plenty of skimmed milk in stock.
Good luck with the op on Saturday!