being 100% honest (knowing it goes against the popular line of thought on here)
For me, that alone isn't enough for me. I did, and still do give my son more things.
That doesn't mean your son won't be happy. it is 100% correct that at 3, he won't be comparing, and basically anything that is wrapped and roughly what he likes will lead to excitement + happiness. It is too young for potential disappointment.
It also doesn't mean you should do more. Gift giving/treats/presents etc. are one part of a larger equation that can foster generosity, kindness, gratefulness or materialism, greed, selfishness, jealousy etc. in children. I'm 100% aware that my family's tradition of doing a lot of presents, in isolation, isn't great, and is on the side of materialism/greed... so for me it has to be counter-balanced by a whole lot of other positive actions/expectations. The result is that we have a dynamic of - you get a lot, but you have to give a lot. It balances, and non of us have ended up horrible ungrateful adults.
I had an ex, whose family were also balanced, but in the opposite manner.. they gave little to each other, but they expected little back, and were all happy. It worked well for them.
The parents that end up having trouble are the ones who give a lot, and have little expectation back from their children. They don't set standards early, no thank you cards/notes, no handmade presents for family, no encouraging the children to plan to do nice things for older relatives, no watching people open presents and letting the child see the joy they have given someone etc. Just a massive mound of presents, and all Me me me me.
So, my point is - figure out the balance of your family. Any 3 year old would be happy with your gifts.. if you do want to do more great, but at 3 - they are old enough to start positive habits to counter the overly-greedy/materialistic aspect of Christmas.