Ahhh... lol. Yeah, you can't do that. Just put each one on it's own line without any delays in between. It will happen so fast, that it will appear to all turn on at once. The human eye couldn't capture it.
Also, if they are all using the 8 bits (you have 8 letters) of one port, you could just do this:
PORTn = 0xFF and that would turn on all bits at once. n = whatever port they are on. PORTD is pins 0-7. But you will lose your serial port. If you aren't using it, no big deal. It's the only full 8-bit port available.
However, my first suggestion would happen so fast, the results will look the same.