Old not bold: Your assumption about your father's first raid is probably about right. "The bomber will always get through" had been a widespread belief through the 20s and 30s and, once Germany had invaded Poland, President Roosevelt made an appeal to the European nations likely to go to war not to bomb towns or civilian targets, and both the UK and France had agreed. (Germany apparently waited till its Polish campaign was complete.) The net result for Bomber Command was that in the first months of the war it could not attack targets inside Germany; only leaflet drops were allowed there. Attacks on German naval ships were, however, permitted, providing the vessels were at sea or moored away from quaysides. So, in a sense, it was the only offensive option available at the time, and the daylight ops on 4 September experienced a near 25% loss rate, a harbinger of things to come.
Middlebrook & Everitt's "Bomber Command War Diaries" gives a good deal of detail on all of this.