I’m not exactly the perfect role model when it comes to talking about career choices. I’ve never had any idea what I wanted to be when I grew up. Still don’t, in fact. So I find it fascinating to watch how my two sons are developing in terms of what they like and the underlying preferences that reveal how different they are.

The theoretical one

I’ve written before about how Isaac (now 5½) is all about establishing, understanding and following rules and regulations. He’d make a great health and safety inspector, complete with hard hat and clipboard.

At Legoland last week he did the Driving School, where kids drive little electric cars around a road course complete with junctions, roundabouts and other traffic furniture. Isaac, of course, is the one child who listens attentively to instructions, always drives on the left, stops at stop signs, checks carefully in both directions at T-junctions and gives anyone who doesn’t do the same a stern ticking-off – even kids twice his age and size.

Underlying all of this is a love of intricate detail, an engineer’s eye for design and the thoughtfulness that comes from being the oldest of three siblings. Last week he returned from an afternoon out at the park and started sketching out his design for his perfect playground, taking into account his favourite parts of the various parks he frequents and throwing in some unexpected flourishes.

You might be able to make out the model village (based on Bekonscot in Beaconsfield, the oldest model village in the world, fact fans) in the top-left corner, and the sand pit, flying fox, roundabout and swings along the bottom. But he has also thoughtfully included a baby play area (for little sister Kara), benches to sit on, ample parking for both cars and baby buggies and an area for kids to store their shoes while playing on the climbing frames and other soft-play equipment. He talked me through his meticulous plan with impressive clarity of logic and no small amount of pride.

I suspect he has already submitted the planning application and is even now shortlisting contractors. It’s like an episode of Parks and Recreation where they actually get something done.

Isaac has gone through many phases over the past two to three years. For a long while everything had to be pink, then there was his ballerina phase, but while some of his favourite pastimes have burned as intensely as a bonfire and died down almost as quickly, his ongoing preference for order and detail and suggests that he’s more of an engineer than an artist.

The practical one

Compared to his cautious, rational brother, Toby (nearly 3½, but thinks he’s 5½) throws himself headlong at the world with barely a thought for his own personal safety and only worries about rules so that he knows when he is breaking them (usually with no small amount of glee).

Whereas Isaac is more likely to pick up the iPad to play a strategy or puzzle game (such as the tablet version of Rush Hour, which I wrote about last week), Toby’s current obsession is the dressing-up app Toca Tailor. (To be fair, Isaac quite likes it too.)

Where Zac is of a more theoretical bent, Toby is definitely more hands-on and practical. Isaac fusses over details, Toby is content with broad brush strokes. Toby’s physical co-ordination is definitely superior to Isaac’s at the same age – he has a noticeably greater aptitude for throwing, kicking or catching a ball – and he seems more comfortable independently drawing and making things too.

Is he going to be the next Paul Smith or Ozwald Boateng? Probably not. But it wouldn’t surprise me if he ended up doing something creative that requires him to use his hands more than a keyboard. Wrecking-ball operator, boxer, croupier, that kind of thing.

Together the boys make quite a formidable team: Isaac designs concepts and creates a set of rules around them, while Toby gets on with the doing and pushes the boundaries by challenging whatever rules are in place. They definitely bring more out of each other than if they were playing alone – the whole is more than the sum of their parts – and when they’re playing together well and not fighting (about 85% of the time), they can be quite happily left to their own devices for long periods, to the extent that prising them away for dinner, bedtime or going out can be quite a battle.

Of course, if there’s one thing I’ve learned, it’s that just when I think I’ve worked out what the boys like it will change in the blink of an eye. But I’d say there are definite patterns emerging in their behaviour that suggests that neither wants to have the old-fashioned ambition of being a train driver when they grow up. Isaac might design a new rail network, and Toby would probably take great delight at sprinting across the tracks playing chicken with trains while his brother chases after him telling him it’s against the rules, but that’s as far as any association with trains is likely to go.

Whatever our boys decide to be, though, I hope it’s something they’re truly passionate about that fires their imagination and enthusiasm the same way things do now. Ultimately that’s what we all want but so many of us ever rarely achieve.