Health insurance isn't cheaper if you move your family to one policy or another,as due to community rating, rates are generally set in stone (although health insurers often offer 'sale' prices).
Regarding your own plan, its hard to comment without knowing your exact details but I have found the Aviva Business plan hospital to be a good plan. It compares well to the old VHI plan B policy and costs approx €900. Your wife and son may benefit from reviewing their cover as well.
The WE plan with day to day cover has built in GP etc. cover which may be overkill if they have a medical card.
If your wife also moved to the Business plan and you moved your son to the Health Value plan (currently on sale from €189 for a child) you could be looking at a saving of over €1000, so well worth checking these plans out.