Is this correct "Could you take your sleeping bag when you come camping with us"

The sentence is correct.

In this sentence, we use "could you" to express a polite way of asking a friend to take his/her sleeping bag when he/she comes camping with you. It also expresses a possible future willingness to perform some action. In this case, we could also use "would you" as an equivalent for the polite way of asking someone to do something.