Months.... lololol. Can't say a little over 2.5 years old?
But like everyone else said, Fire tablet
Kids fundamentally change a lot in their first five years of life and especially the first 1000 days (first 9 months of pregnancy and first 2 years). This is when the brain makes lots of fundamental changes during this time with scientific terms such as neurogenesis, neural migration, neural differentiation, synaptogenesis, neural apoptosis and the start of myelination and start of synapse formation and the refinement of synapses.
All of these steps besides doing stuff with the brain actually causes changes in behavior noticeable in the baby/toddler. After year 3 though the timescale is more appropriate to probably use years and fraction of years.
Most people that interact with the kid daily or weekly during these times notice these differences in behavior but to outsiders whether your kid is 24, 27, or 30 months is useless and trivial info.
sigh... this is what your toddler needs...
Hard to do in a moving car but your logic is sound in other places. Once you reach the hotel or the friend's house in which you are visiting you should switch to these and take the tablet and other electronics away from them for later (saying you are charging them when the child starts to wise up around age 4 or so), to engage different brain areas involved in motor control and sensory processing that are changing the most during the toddler year.
There are fundamental difference between pointing with your fingers and hand and manipulating the fingers around a crayon or other object. My mother is an occupational therapist who works with toddlers and young children with disorders that makes this harder (think autism, coordination disorders, etc) During the first few years of life you can train and improve certain skills that are much harder if not impossible to change later for during certain key ages of brain development your body are turning on genetic switches that allow you to rewire the brain to some extent which at a different age the genetic switch is flipped off.
So to the OP please please focus on things like sensory exploration, exploring new environments, things that the kid interacts with both close and far away and so on.
Fun fact but it is not just the brain that are making key changes during this period but also things such as nearsightedness. The eye does the majority of its formation during these years and depending on the amount of light it is exposed to determines factors of the eye such as its preferred distance focal point and now easy it is to track movement. Long amount of times indors encourage nearsightedness for the amount of light that hits the eye is far less than outside. Human adults do not notice this for like cats we can change the amount of light that hits the eye's retina and thus we can make dark rooms seem brighter just like a cat can see in the dark. Well the amount of light hitting the eye during the toddler years helps determine how the eye forms by fine tuning turning off and on specific DNA genes by a process called epigenetics, epigenetics puts another way is environment and genes interactions.
Nerd rant over