Can the officiant be a witness?

It really depends on the local county or jurisdiction where you are getting married. Are the two witnesses you mentioned what is required in the place you are marrying in Iceland? If so, try asking their equivalent of the marriage license department for confirm for sure. You will get varying answers on here as all locales are different (i.e. some places do not require a witness, some do not allow internet-ordained officiants, etc.). Unfortunately, there is no "definitive answer."

Right. This would be Iceland.

I gotcha! The two witnesses are required in Iceland. I wasn't sure who to send this question to. I will contact their license department! Thank you so much, this really helps.