Age and conditioning have little to do with it. Won't know how you are at altitude until you go there a few times...and even then, there is serendipity, people have off days, etc.
You are climbing very high and altitude is a significant issue. The portal could be enough or it might not be. But you have the option to do 2 nights at 9.5K or 10K (OV or HM) and another at 12k (Trail Camp), so why not take it? That is a fabulous pre-summit profile from an acclimatizing point of view (though still not a guarantee, it's all relative). Plus those other locations will get you seeing some cool areas.
Other tips: keep hydrated (seriously), take electrolytes, and don't overdo it (good to hike at a pace where your breathing is steady and your heart is not racing). Slow is better than fast. If you search this site, you'll see a lot on this issue. Someone will now suggest diamox, but I'm gonna leave that topic alone since it has already received tons of coverage on this site. Also, on Monday, while you don't want to overdo it, climbing higher than your sleeping altitude is a good idea.
