I did a solo trip from EP #50 to Poplar back in the fall of 2012 - see my trip report for information. I went across from Long Island to Muskeg, Kiskadinna, Omega, Allen, Horseshoe. A couple of tough portages in there, especially for newbies; pack light and whip them into shape beforehand ;). Omega's a nice lake, Horseshoe too. Nice paddle down Cross Bay. You'd have time for some side trips. If you have any questions, just ask.
You can also take the northern route through Banadad, Rush, etc. The portages between Long Island Lake and Banadad are kind of tough, also no campsites until you get to Banadad. Some portions experienced a fire a few years ago. The long portage at the end is easy. We used Tuscarora Outfitters for a shuttle, they're within walking distance of the Cross Bay Lake EP. There's a beach at the end of the portage from Karl to Long Island Lake. You can walk there from the Karl Lake campsite. I believe the site on the LIL side is on the beach as well. There are lakers on Karl and LIL.