What exact CN variant will you be using? An initial CPU-only mining period might entice additional miners.
The latest ASIC proof version of CryptoNight, which I believe is V8.
I don't think there's a way to make it CPU only mineable, but CPUs are very strong in this algorithm, so the cost-effectiveness of having a multiple GPU rig won't be worth it to most miners.
This promotes decentralization in mining during the initial stages because only one computer can be a miner at a time, before larger farms will (if ever) be set up.