i don't see any problem of tying into the same fuel head for the kicker.
i've done it on a couple of my boats and had no issues.
ideally, having a separate fuel source gives you added security should you develop a fuel issue that fouls your motor(s), but IMO its just too much a PITA to have a separate tank than the main to feed a kicker. Use the Racor or similar with clear fuel bowls and regularly inspect your bowl(s).
use a higher quality thread tape (fuel, hydraulic or gas tape) than just teflon tape to ensure a good seal. The stuff is usually similar to the white teflon, but yellow in color and a bit more $.