First, I want to reassure you that many children do not develop a clear hand preference by 2Â½. Your son may well be in that group. I would not try to change him to his right hand if you are convinced that he strongly prefers his left. If he wavers, or uses one hand some of the time and the other at different times, you could encourage use of the right hand and see what happens. For now, base your actions on the evidence offered by the skill level he demonstrates with each hand. You indicate that he is awkward when using his right hand, and that fact should be fairly persuasive with your husband. Of course, he may turn out to be truly ambidextrous (and have a great future in baseball). But whatever you do, don't make a big issue of it and force a change. That can create far more problems than just being left-handed.
As for poor handwriting, there is no evidence that the penmanship of left-handers is consistently worse than that of right-handers. And there are plenty of famous and successful people who are left-handed —President Clinton and the first President Bush, to mention a couple.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.