Having single handed the L&L many times (like you, small child on board so often boat as if single handed!!). The easiest way I have found is, as outlined by another post; if you can't stop at the bridge on off towpath side (i.e. the side of the bridge you have to operate it), stop on towpath and walk over bridge with a long bow line in your hand. Unlock and open the bridge, pull bow over to you, hop on boat and motor through. Stop on other side and get off stern with stern rope in your hand and close bridge (can't think of any that are too hard to get back too to close, although sometimes a bit of a clamber as you will be off towpath side). Close and lock bridge. I never tie my boat to anything, just make sure you can either keep hold of the rope (loosely) or lay enough out on the ground that if the boat drifts, there's enough to grab and pull boat back.
Anyway, if you pass Meridian round Skipton, give us a shout and I'll pop out and do bridges for you.
It sounds harder than it is!!! Just take it steady and take care if it's wet.