Personally, I suggest completing a few more sprint triathlons and at least one olympic distance tri prior to completing a half ironman. In particular, given your lack of swim and bike competitive experience and with less than 10 weeks of training, simply attempting to put in the number of yards in the water or miles on the bike greatly increases your risk of injury. I take it you are young and still healthy, but injuries occur in young athletes nearly as often as in older athletes because of lack of planning and over training. Perhaps you are older than I perceive. But even the oldest or most experienced and healthy athletes prepare for this multi-sport distance months in advance.

According to your running history, the run will be your strongest and easiest leg of the race. Thus, you should focus your preparation on the other disciplines and on the transitions. Your body needs not only to compete in each discipline, but also it needs the training to adjust to the changes of body position and muscle-group focus. This is NOT like working out at the gym moving from arms to back to legs to... The sport of triathlon is a sport of its own, regardless of your abilties in each discipline.

I was a competitve swimmer through college, but it still took some adjusting to the open water. I don't know what your stroke looks like, but open water swimming for me requires a much quicker stroke rate and less "reach" in the front than my distance swimming in the pool. Also, bilateral breathing is a must so you can keep your bearings amongst the field of competitors and the race course. My tip for the biking is to increase your weekly milage and to know what your pace is. Also, be sure to do brick runs after your long rides. This will help your body become acclamated to the transition.

You can still train with your friends but if they already have put in substantial yards and miles then it is best not to equal their training output. Focus on transitioning from the bike to the run and after a swim, hop on the bike, just to get the feel. If you are able to increase your distances up to the required distance of the half iron within ten weeks, then be very cautious of injuries.

Be certain to stretch all muscle groups thoroughly. Warm-up in each distance at a slower than comfortable pace descending to a comfortable pace. Always warm-down; rule of thumb from my best coaches is to warm down at least 20% of the distance done at your competition pace (REALLY!). You should ice-down sore areas before inflammation occurs. And should you reach that point, talk to your doctor/pharmacist about the proper use of anti-inflammatory medications, such as Advil (ibuprofen) Aleve (naproxen) or Celebrex (celecoxib). Over the counter NSAID's can help tremendously if used safely, and generic prducts are just as effective and safe as the brand names.

It's also important to consider hydration and nutrition during the race and training. This discussion is an entire topic on its own. I'm still a die-hard fan of "Eat to Win" from the 80's. A lot has changed since that time, but the basis of the book is superb. You should definitely consult experts and experienced iron-distance athletes to develop your plan. There is no one best way to approach training and nutrition, but it is a personal balance of tried and tested methods incorporating advice from experts.

In any case, I suggest signing up for a few shorter distance races in
the near future - again to acclamate your body to the sport of
multi-sport. I wish you much luck and health in your training and competing!