Sounds to me like deep down, you *want* to solo but you just need a push to convince you it's OK...or maybe it's your friends that need convincing that you won't slow them down?

Soloing isn't nearly as difficult as it seems when you've never done it.  I was a diehard tandem canoeist until last year when it was either solo or stay home for me.  I took a 9-day solo trip and I'm very glad I took the plunge (figuratively speaking only).  Up until the moment I shoved off I had no experience in a solo canoe.

The butterflies lasted about halfway across Inlet Bay on Basswood.  After that I felt very comfortable.  I tried a double-bladed paddle but that style of paddle uses different muscles, so I switched over to a single-blade and didn't lose all that much speed.  

I'm in decent-but-not-fantastic shape for my age and I had little difficulty keeping up with tandems that were heading in the same direction as me down the S-Chain.  They weren't racing me or anything, but they weren't loafing around either.

I got into some hefty headwinds and was still able to keep a decent steady pace of travel.  I even accidentally got into some surf that only an idiot would try to canoe thru and I managed to stay afloat until I could reach calmer water.  The key is to stay loose in your seat, keep your torso centered and vertical and let the canoe roll with the waves under you.  The canoe WANTS to stay upright.  Usually when it doesn't it's because someone panicked and made a dumb move.

4 travel days on your loop is not going to kill you in a solo, either.  I've done that same loop several times and none of the days is particularly difficult.  You'll do just fine.

I'm in a party of 3 this year.  A tandem plus me in a solo.  I can't wait to get out there again in my own canoe!