Interesting situation you have there. There are many upmix algorythms around in stand-alone software or plugin form. I personally have more experience using the TC System 6000 algorythm, but most pro options do a very commendable job. Where your situation gets tricky, and thus interesting, is that you start with a binaural recording, which has no crosstalk between left and right channels. You will get a surround mix out of an upmix algo, but it may sound a little weird, as those algorythms are based on a "conventional" stereo input. And as far as creating your own upmix, the problem isn't solved as your binaural sources would need to be somewhere between your L/R and Ls/Rs pairs. And then it just gets more complicated.
What I'd suggest is to process your recording using an upmix algorythm and see how that sounds. If that's not satisfactory, or if you're curious like me, you could try to bleed a little bit of each channel into the other in a DAW. I'd go for relative levels of -3dB, -6dB and -12dB of bleed and reprocess those in the upmix algorythm and see what sounds good. If you get there, it'd be cool if you could post about your results. Just be careful to check that your source doesn't have low-frequency rumble from wind or mic manipulation, as is common with binaural recordings. If there is some, you should filter it before upmixing, as it may screw with your LFE channel output. You could also look into the surround alternative for binaural: http://www.holophone.com/home.html
Since articles about upmixing from binaural to surround gives the impression you could get a faitly "realistic" result I was expecting/hoping those algorithms were implemented somewhere. I thought there should be a market if poor lads like me could make surround mixes using homebrew binaural microphones instead of expensive surround mics.(I would love to have that holophone mic you mentioned but my wife would kill me if I spent a full year of our savings for that.)
But until I get hold of any dedicated binaural upmix software I will start looking for some standard upmix plug-in or software and give your suggestions a try.