Due to lack of overall mobility and the potential for tangly-sharp stuff in the river, I would not recommend float tubing. Current, wind and sticks make a dangerous combination when your legs are hanging down below. If you got hung up in deep water, the only way out is to roll over and swim or detach the seat and slide under. If you can't stand up that means swiming.

A buddy of mine was snorkeling the Satsop observing fall kings. As he was free drifting down, his swim-fin buckle snagged on a unseen root wad. He was instantly forced under a cut bank fully extended and couldn't curl up enough to reach his ankle. He would still be there if a companion hadn't seen the whole thing and followed the same drift freeing his leg as he drifted by. Totally lucky!

I have used float tubes for duck hunting and fishing, so far without incedent ( except the time I was duck hunting and a mink-like creature thought I looked like a muskrat den).
However, I am always carefull and never really feel comfortable or safe just one fastex buckle away from swimming.

Good luck!