Hey there Teigyr... I be erring on the side of caution with your partner. I'm not a runner, never have been, but my partner was and I guess I can tell you a bit about his experience...

He used to run marathon distances, he is your age now... but he stopped running at about 30 because he just couldn't take the discomfort anymore.

He pretty much wore his worn his knees out.

Now, any time he does alot of walking - particularly down hill... and the few times he does run (like on our family sports day) he suffers for several days with the pain.

I would suggest, try the half, see how you feel during and in the recovery days, before you sign up/pay for the whole. But undertake the committment to yourself - if you really want to do the whole, tell yourself that completing the half in good form means you must sign up for the whole.

I anticipate hearing that you did the half and did it well, and feel really good about it/your body.
My man loves to run and he still really misses being able to do it.