Why should volatility be problem?If you are so afraid of the Bitcoin price fluctuations,than why not just sell your bitcoins for fiat,right after the buyer pays you with BTC for the domain name(after 3 confirmations).
If you ask me,BTC price volatility won't be your main problem.Your main problem will be finding buyers that are willing to pay for a domain name by using Bitcoin.
By the way,do you plan to use a crypto payment processor,like Bitpay or Coinpayments?
I think the best option is to have a crypto payment processor. There is one good thread about it that maybe can help the OP to decided in the future,
Bitcoin Payment Processors. Volatility will also be present in crypto, it's just how you are going to manage or mitigate it.
The link might be broken, won't direct me to the thread.
Anyway, I think OP's business is not big enough to use a payment processor or a third party service, enough knowledge on bitcoin volatility would probably make him minimize the risk, and of course he can do it manually by trading on stable coins at the end of the day, or any period he likes too, besides volatility does not only mean you lose, you could also win on it, especially if the market is bullish.