It isn't your job to stretch him or compare him to other toddlers.
Sorry, but I heavily disagree with that statement. Of course it's my job to stretch him and comparison is necessary to see whether he is developing the way he should.
Without being stretched he wouldn't progress in his development; he needs new experiences and new challenges all the time. I've noticed that he tantrums a lot more if he doesn't have anything to figure out or anything new to do, almost as if, once a new skill is mastered, he is ready to move on and if I don't keep up, his behaviour gets worse.
Just to pre-empt, that doesn't mean that I constantly over-stimulate him. He is quite happy just to play on his own in his room for an hour and will role-play with dolls, toy food and toy tools, just as much as he will 'read' books, dance to music, jump and climb all over the place.
All you need to do is talk to him, play with him, work out what interests him and give him lots of varied and stimulating life experiences.
And that is exactly what I do. The dilemma (if you can call it such) is more that some of the stuff he wants and needs is just not age-appropriate. For example, when we watch music videos or listen to music in the car, he is not interested in children's songs bar one or two. Instead, he actively asks for Queen and Metallica songs. Some days he wakes up and the first thing he says to me will be "Queen - We will rock you".
And while it's all cute with songs, other things are harder to cater for, because he is still so young and small. Like go on rides or to a trampoline park. He has the height of an average 1-year-old and still fits into 12-18m clothes, so gets refused on H&S grounds. Understandable, but difficult, given how much I know he'd love them. Indoor and outdoor playgrounds work well when there are not many people, but when it's full a lot of children take advantage of his height and push him out of the way. He is too small and gentle to muscle his way through.
Or toys. He has a few toys he loves (guitars, dolls with equipment, his toy kitchen, Lego Duplo), but he prefers playing with toys, which are clearly labelled 3 years+ due to small parts. Do I let him play with them (supervised) or do I follow the guidelines and, essentially, hold him back?
Like I said, he is starting to recognise numbers written down. He points them out to me in shops and around our home. So does that mean he is starting to make a connection between written symbols and letters, too, and I should encourage him to 'read' (not proper reading yet, but just the concepts of a few words sounds frighteningly wrong with a child that young)? We read books all the time and he will talk along and point at things and tell me what they are, or remember passages from (simple - like Little Princess) books and talk along.
The funny thing is that he's my third. First child was developing age-appropriately, second was a little advanced (but has Asperger's, so struggles socially), but his development is just off the chart and I feel a bit like a first-time mum again.