I am in that general area and there is LOTS of overflow in places and lots of leads opening up on the river. The snow is really slushy and unless you have a paddle track or something you may spend alot of time fighting it. I got stuck so many times on my trapline Wed that I gave up and backtracked home.
I would be really cautious about the crossing from the mouth of Kashwitna across the Susitna. It froze late and this warm spell really has the ice going fast.
You could give Ron over at Susitna Landing a call, he will know the river conditions there.