First off, let me welcome you to Ubuntu as well as Linux community. I'm elated that you're having the intentions to teach Linux to your young son (I wish I'd have picked linux that early in my life).
My answer is based on the assumption that you're a new Linux user, and the primary intent is to use your machine for home (causal) computing.
Given below are few points(I wish I'd have know when I started) which I hope would be enough to give you the right direction, from where you can chose to make your preferred opinion:
Linux world is vast, and presents a gazillion options to chose from. Most of the times, instead of empowering a 'new user', this plethora of choices overwhelm the user to go back to the familiar world of Windows. Don't overwhelm yourself.
One of the goals with which Ubuntu is developed is to not overwhelm the users, and just get them starting. Ubuntu has several flavours (Lubuntu, Kubuntu, etc) which offer different Desktop Environments (DE). In crude terms, Consider DE as a skin/wrapper to present you with a User-Interface to the underlying system which is same for all flavours. Underlying system is easily accessed via command line (terminal).
- There are other distributions, few based on Ubuntu itself, which are trying help Windows users migrate seamlessly to linux. One such distribution is Linux mint.
Most likely you've chosen a stable version (Unless your downloaded .iso file has beta/alpha in its name). Read until the end to find about the command lsb_release -a
A stable version is ready for public use. Depending on how long they'll receive updates (feature/security/bug-fixes), There are 2 types of stable releases Ubuntu offers.
Windows software won't work on linux due to different architecture. This doesn't mean that you don't have alternatives. Most times than not, your Ubuntu will already have pre-installed softwares for what you're trying to achieve. Additionally, you can search the name of an Ubuntu equivalent software for the task you're trying to achieve. Chances are you'll find an open-source, free, stable, and easy to install alternative that just works.
Consider upvoting and accepting my answer if it helped.