OK, thanks for the advice. Tyre levers were included, just forgot to name them. I have repaired flats enough time to do it consistently. Never with a coaster brake, though, but I assume it's just a matter of unscrewing the bolts and screwing them back when the flat's mended.
Then, more water (I'll buy a litre bottle), and another kind of food, if any. Cookies perhaps?
I think I'll have to get a big saddle bag or carry a small backpack, else I won't be able to carry everything.