My brother has been riding with his kids for a multi-weekend trip on road bikes. They are going to ride down the California Cost from Ventura to San Diego. Unfortunately, my brother hit the deck and broke his elbow today. He has had this trip planned for over a year and the rooms reserved, kids all ready, time off work set, and then this.

Anyhow, I told him that a bent might allow him to still do the trip. The kids ride rather slow and don't climb too fast. He is open to the idea. So I need some help/tips about how this might work. What style bike should I look for? His budget is around 500 bucks so it will be a used bike...from Bakersfield CA or San Diego CA. (Craigslist cities we can buy from)