The Cog trains run every 80 minutes but they only spend 30-40 minutes at the summit and you must take the same train down. If your husband misses the 30-40 minute window when the train is there, you are out of luck. Driving gives you more flexibility; you can leave earlier and be at the finish line. Pikes Peak is a major tourist attraction and if you can do both, go for it. However, there are some risks. Altitude sickness can be an issue; it affects everyone differently, and it is hard to predict who will be affected. Also, driving the Pikes Peak highway can be a terrifying experience for some flatlanders who are sensitive to heights and driving mountain roads. If weather becomes an issue, you can always be cautious and wait in the tent in Manitou. Don't forget to bring some warm clothes and expect to wait at the summit in 50 deg temp with 15-20 mph winds.
