There is a ton of discussion about this on one of the other boards that I'm on (where they specialize in burning wood, instead of cutting it up...) and the whole question of OWB's is a bit of a sore point...
1. "Standard" OWB designs tend to be very inefficient, meaning that you both go through a LOT more wood, and make a great deal more smoke pollution.
2. There are a lot of people that burn green wood and some that burn trash, old tires, and other garbage that makes the pollution problem even worse. Unfortunately there are some OWB manufacturers that aggravate this by implying or even advertising that it's OK to do this.
3. Because of this pollution, there are a lot of complaints from neighbors, especially when an OWB gets put in a more crowded area, leading to the governments at different levels trying to "solve" the problems via regulation, and making life difficult for the people that are trying to operate responsibly, or use wood stoves, etc.
4. As mentioned, a standard OWB tends to need more fuel than an EPA woodstove, and generally bigger peices, if you are worried about the ability of your elders to handle the wood, this is NOT a direction you want to go...
What I would suggest is that you should avoid "standard" OWB designs - which are essentially a firebox surrounded by a tank of water.
What I would look for is a "Gasification" wood boiler - A couple of brands I see advertised heavily on ********** are EKO and Econoburn, there are others, many of them from Europe where pollution is a big deal, and they are concerned about getting as many BTU's out of a chunk of wood as possible.
Many of them are designed as boilers for use inside a building, but this is no big deal, it just means you need to supply a shed to put around them (and many folks use this as an excuse to build a larger building that combines the boiler space with wood storage and / or workshop space, etc...) or put them in an existing outbuilding.
A gasification unit will burn much cleaner and more efficiently by virtue of it's design, and most use stove wood size splits (which do need to be properly seasoned) You can get even more efficiency and cleaner burning by incorporating a thermal storage tank into the system - this way the burner runs flat out (it's most efficient mode) as much as possible while dumping any extra heat into the storage tank, and then you heat off the tank for a while before needing to build the next fire. (Lots of details on how to do all this in the "Boiler Room" on **********)
I think you and your parents would be much happier with a gasification unit, as it would better fit their needs - burning efficiently takes less wood, and you can still put it out where it will be easier to load.
Gooserider