Every year around this time I am asked some version of this question: should I (or should my child) get baptized at camp?
It would be difficult to defend an absolute prohibition of baptisms performed outside the confines of the gathered church given the descriptions of early Christian practice within the New Testament. The Ethiopian eunuch, for example, was baptized in a river on the side of the road:
And as they were going along the road they came to some water, and the eunuch said, “See, here is water! What prevents me from being baptized?” 38 And he commanded the chariot to stop, and they both went down into the water, Philip and the eunuch, and he baptized him. (Acts 8:36-38 ESV)
Likewise, we could cite the example of the Apostle Paul who was baptized in the house of Judas on Straight Street (Acts 9:10-19) or the household of Cornelius who were all baptized on his private estate (Acts 10:44-48). The Philippian jailor, along with his whole household, was baptized at his personal residence (Acts 16). The same could be said for Lydia in the same chapter. In fact, it is difficult to think of a single example in the New Testament of a person being baptized in the presence of the gathered church.