Question

What arguments should i pass to wait() so that it waits for all child processes to terminate before continuing

Answer 1

wait only waits for a single child. You should call wait(NULL) in a loop until it returns -1 with errno == ECHILD:

while (wait(NULL) != -1 || errno != ECHILD) { }

From the wait(2) manual page:

ECHILD (for wait())

The calling
process does not have any unwaited-for
children.

EINTR

WNOHANG was not set and an
unblocked signal or a SIGCHLD was
caught; see signal(7).

As such, you must check for ECHILD, lest you be fooled by a caught signal.