Scooters that have the bigger all terrain wheels will also require a vehicle to carry them in as they do not fold. Power wheelchairs with the all-terrain wheels are also heavy and require a vehicle to hold them. If you are going that route you need to determine whether he needs a seat that reclines or tilt-in-space. Again they all are heavy and require a lift to get them into vehicles and vehicle large enough to handle them. Only you can determine how often it will be used and whether the investment in vehicles is worth it. Assuming you have a vehicle and are going this route, you can try Craigslist for scooter and then research those you find. You will need to be mechanically inclined to service them or hook up with a local dealer who can sell you new batteries, etc. If grass and gravel is only a problem once or twice a month, you might consider using a wheelchair for those times or a rollator with 8 inch wheels for outdoor use - one that could be used by him and or pushed by you. http://www.1800wheelchair.com/asp/view-product.asp?product_id=5090