Can. 932 §1. The eucharistic celebration is to be carried out in a sacred place unless in a particular case necessity requires otherwise; in such a case the celebration must be done in a decent place.
§2. The eucharistic sacrifice must be carried out on a dedicated or blessed altar; outside a sacred place a suitable table can be used, always with a cloth and a corporal.
So the question is whether the circumstances of his visit really create a sort of necessity to celebrate outside of a church, or whether this is merely desired as a convenience.