An easy start…

Connections to lived-in world

You can connect children's lived-in world with how you'd like them to represent and reason about kinematics by starting in two dimensions. Such a starting point also makes it easier for you to introduce the kinematic quantities. Learn to love reasoning with arrows to reduce your worries about making such a change in your teaching. This assumes that you currently follow a more-or-less conventional approach in starting with relationships between speed, distance and time and then relying on graphical representations to support much of the discussion. ggg tasty

Five supports

There are five supporting lines of argument for this approach, each of which is, in effect a pedagogic suggestion, being an interpretation of current research evidence and successful practice:

That taking a point of view is essential for recording or noticing a motion or change in motion.
That starting with accumulations, and reasoning about accumulations, is a much simpler approach to looking at the kinematic relations that thinking about operational definitions based on rates which rely on calculations of differences and then divisions by infinitesimal times.
That starting with simple pictures of journeys, from a drones eye point of view provides accessible and fruitful hooks, as much everyday depiction of and discussion about journeys is two-dimensional, from verbal instructions to sketch maps to GPS-enabled tracks and route-planning.
That we make use of vectors as our primary tool for representing motion and delay representing motion on Cartesian graphs until kinematic ideas are well-established, as reasoning with arrows can be rather simple.
The widespread availability of motion sensors linked to the representational power of software, in particular for position and acceleration, allows you to choose which quantities might form the basis for kinematics and how to represent them. You need no longer rely on ossified decisions in the era where only metre rulers and stopwatches were available.