I discovered an odd convergence about Ironman Coeur d'Alene...
In the northern hemisphere in the summer, the farther north you go the more daylight hours you have. And the closer to June 21st, the more daylight. CDA is one of the more northern Ironman races and takes place on just about the longest day of the year. Which means this is one of the best races to try to finish during daylight hours.
According to online charts, sunset should be at 8:51. That's a sub-14-hour Ironman which is a little fast for me but it might be a goal for others to reach for. (Besides the main goal of just finishing!)
Ironman Canada is farther north but takes place later in the summer and sunset is at 7:59. Your best bet seems to be Ironman Germany on July 6th, where sunset will be at 9:36 pm. Other good races are Ironman France (same day as CdA) with sunset at 9:16 and Ironman Switzerland July 12th, 9:20pm.