Use the simple present tense with in case to talk about a possible future event!
e Take a spare pair of running shoes, because it's possible that you will need them.
Take a spare pair of running shoes in case you need them.
f Take a waterproof coat with you because it's possible that it will rain.
Take a waterproof coat with you in case it rains.
g take a warm jumper because it's possible that you will get cold when you stop.
Take a warm jumper in case you get cold when you stop.
h Take a first-aid kit because it's possible that someone will get injured.
Take a first-aid kit in case someone gets injured.
Хотя обычно после who стоит is, но в данном случае у нас дополнение во множественном числе friends, соответственно и глагол ставим во множественном числе