All that preparation for entry through that one point of entry is good, but remember that Mr Murphy is often along for the ride and and well thought out plans will unravel when the **** hits proverbial fan. The fact that you're actually thinking about it puts you ahead of a lot if people. Just don't focus on that one point of entry...gameplay in your head for other contingencies and have plans for them as well.
BGs are opportunists and cowards for the most part...they want to prey on the easiest targets who will offer the least resistance. Make yourself and your home a less attractive target with extra security features, such as an alarm system, dogs, extra lighting inside and out, better locking mechanisms and security at possible points of entry, etc. Your local Police Department's Crime Prevention Unit (or similar) will often offer free security assessments of your home or business. If the BGs deem your house to be too much of a hassle, then you've won before the battle has even begun! That's the real goal...to prevent it from happening in the first place!
As far as reinforcing your children's bedrooms, others have provided very good solutions.
I would add that in a dynamic critical incident, such as an intruder, armed or not, in your home, your adrenaline will be pumping and fine motor skills will become much more difficult. Your body will fall back only on training that has been ingrained repetitiously. You need to become proficient with whatever weapon you choose for HD. Not just bullets on paper statically at a range, but you need to become combat accurate vs bullseye accurate...that is to put as many hits on target as quickly as possible to put that target down. Spend the money and time on a real class with a good instructor to get exposed to what it's like to engage in a stressful firearms encounter. Learn your own strong and weak points so you can improve. Your life and that of your family may depend upon it some day.
I also strongly recommend and urge that a weapon-mounted light be used on any and all HD weapons. A quality bright light can be used offensively by momentarily blinding your foe so that you can gain a tactical advantage, since you will likely be at an initial disadvantage in an intruder scenario. A weapon-mounted light also helps to clearly identify your potential target to ensure that it isn't a family member or friend.
Understand that the above is my opinion based upon my training and experience in nearly 10 years in the military (intelligence and special operations) and 15 years in LE.
My home is also laid out where my bedroom is on the first floor and both of my children's bedrooms are on the second floor with the only stairwell up located on the opposite side of the house from my bedroom. Hardly ideal. I know that, in an intruder scenario, I may have to fight my way through the BGs in order to get to my kids. They are my first priority.
My primary HD weapons are my duty-issued 9mm Sig P226R with an Insight M-6 light/laser mounted and my 14" 12 ga Mossberg 590A1 shotgun with Surefire 621FA Weaponlight, Hogue Youth Stock, and 3GunGear.com 7-shot nylon side saddle, as seen below: