Lots of good advice so far. Definitely listen to
@DopeyBadger and his numbers. "Da numbas don't lie." (Picture bad accent with that quote)
As for me, check out my training blog under training blogs, and the link in my signature.
On one hand, I was/am a poster child for "doesn't look like a runner" and I tend to undertrain in terms of distances. My training is a lot of shorter runs.
And my first full marathon was part of my first Goofy; so much for a stand-alone. (My only standalone full was the MCM, the other 3 have been part of a Goofy or Dopey). And no lie, the first few miles of that first full, I thought I had a stress fracture in my feet (yes, one in each foot). No, turns out they just hurt from the prior day's half.
A lot of better training and better footwear since then has meant not repeating that level of pain for a challenge. Some fatigue from having run the prior day, but not pain.
Like others on here have mentioned, if you do a challenge, take it much easier on the race(s) prior to the full so that you leave plenty in the tank for Sunday. Can't run it the whole way? I don't. Run or jog the initial miles to build up a buffer ahead of the balloon ladies and walk the rest; a brisk walk is a 15-16 min/mile pace for most. You may not have time for a lot of photo stops, but you'll finish without getting swept.
Marathon weekend registration is 6-7 weeks away. Do you think you are ready ready for a half? If so, see if you can find a local half and see how you do. If not, then train and at least do the full.
One last tidbit: my first ever half was at Disney, and at the time I thought it was one and done. But AORD (adult onset running disorder) set in and I've been back several times. At the moment, I hate the idea of driving down to Orlando for just a single race, which is why subsequent visits have been challenges. That may change when I get older, but it is where I am now.
As always, YMMV. Good luck.