If you want them all to start at the same time why not start them all, delay for 3 seconds then stop some, then delay another 3 seconds and stop the last two? It's crude but it might work.
OTOH using millis() is the proper way of doing this sort of thing. At some point you're almost bound to realise that you wanted the Arduino to be doing something or paying attention to something while the delays were forcing it to do nothing.
Steve