Network booting on different platforms is fine, as long as you configure the right kind of netboot for the hardware you have. i386 and amd64 architectures use PXE for network booting (and DHCP to determine the boot server). Most other architectures use BOOTP. Sun systems use RARP and TFTP. As long as you have the right kernel for the OS you're booting, and you're running the correct daemon, it will work fine. Sun boxen can boot from i386 servers, Macs can boot from Suns, amd64s can boot from i386s (with a 64bit kernel), etc.
It sounds like all your hardware is PC clone, so a mix of i386 and amd64. In that case they'll all use DHCP and PXE. Just specify the right kernel image for each MAC address and you can boot each one with it's best kernel, even if the OS you're hosting the boot images on isn't that architecture.