I'm sorry to hear about Otis, but very relieved to hear that he is doing okay and that he made it though this traumatic experience just fine.
One thing that you could do for both of them for playing in the front yard is get harness for them and them put training leads on them that way there is a long lead on them to just drag around and it's not attached to anything but you can snatch it up or step on it when the time arises. They are both small so doing this wouldn't hurt them or you; and having them on the harness prevents injury to their necks if they do a hard jolting stop. I do this with my boy and my foster too for training (yes with basenjis kinda off leash) and if they get a idea to go off on their own I am able to retrieve the offender.
These are the kind I use, they are rounded so they don't pick up yard/park/trail debris as easy as the second one I'm going to show you. Also with this exact variety if your wayward basenji does what all naughty basenjis do and chew it. It's easy to repair with the rope, a good knife and a lighter. And you'll never know the difference (except it's a few inches shorter LOL). I find it's also not as fast to chew through as the second one too. But then I don't suggest them for tie outs either, only as drag lines/training lines
This is what kind I got,
http://ep.yimg.com/ip/I/morrco_2057_4205673
This is the second variety I menthioned above, you can get ones like these at Petsmart/Petco, they are not bad, but if chewed will snap easy (they can be tied back together and it will hold up just fine again then though, just looks ragged LOL)
Here they are on this site, I just can't find them on the Petsmart/Petco pages, but I know they have them in the 15 or 20 foot length
http://www.morrco.com/trainingleads1.html