If he's asked, just go with it. And if he's not asked for the stabilisers, don't put them on now.
Give ti a go and see how it oges. Expect some shouting and tantrums (when you don't hold on "right", or he falls off as soon as you let go), but you well be surprised by how quickly he "gets" it - albeit not necessarily in a straghit line to begon with.
Ds (nearly 5) was given a bike at Chrsitmas, which he was never particularly interested in, I think becasue it was much harder work than his "Lyke-a-bike", (wooden bike without pedals), which he could fly along on.
Eventually he did give it a go - with stabilisers - and we did a few wee walks aout on it - but still used his "flying bike" (as he calls his wooden one) most of the time.
About 6 weeks afo, he suddenyl asked if we would take his stabilisers off. The following day we did - and we had half an hour (at most) of him wobbling and shouting at us, before he actually got it - albeit for only a few metres. By evening time, he was cycling up and down his grandparents driveway. (My dad helped the porcess by lowering his sadle so that technically it was too low, but while he wobbling and falling over, it helped that he could reach the ground more easily while he was sitting in the saddle).
Give it a go!