What follows is a collection of sources that in some way describe the Karankawas’ missions:
 Bonilla’s Brief Compendium of the History of Texas (Breve Compendio)
Author: Antonio Bonilla
Written In: 1772
Description: Spanish Viceroy Antonio María de Bucareli y Ursúa ordered officer Antonio Bonilla to compile a nearly hundred-year history of the troublesome province of Texas. In fifteen days, Bonilla vigorously wrote a seventy-page document entitled A Brief Compendium of Events in the Province of Texas.
(1) There exists a single offhand mention of the Karankawas in Bonilla’s history. It being the following: “The Carancaguazes Indians were asking to be brought into missions, allowances for ten soldiers were added to the Presidio of la Bahia del Espiritu Santo, in the year 1758; yet even to this day they abide in their heathenism, becoming apostates when the inclination ceases them.” 
(2) Bonilla’s work inspired a far more influential text: Father Juan Agustín Morfi’s History of Texas (See Morfi, 1783). Bonilla’s A Brief Compendium claims that that the colonization of Texas failed because of the incompetence of mission priests. Padre Morfi, an accomplished Franciscan friar, became so incensed upon reading Bonilla’s conclusion, that he spent the next decade writing his own history of Texas—this time blaming Indians, presidials, and the Spanish government for Texas’s failures. Morfi’s text is a particularly propagandized depiction of Karankawas.
Access: Antonio, Bonilla, “Bonilla’s Brief Compendium of the History of Texas, 1772.” The Quarterly of the Texas State Historical Association 8, no. 1 (July 1904): 3-78.
Further Reading: I can not think of any, do you have ideas?