IF you are staying at at value or moderate resort and IF you have 2 children under the age of 10 in your party, then the VISA package is better than booking separately.
The room rate will be at the rack rate, making the cost of staying at a deluxe too high in comparison to other discount rates. And if there is only one child under 10 in your group, only their UPH is free. You will have to purchase adult UPHs for anyone in your party over the age of 10.
As 4greatboys stated, children under the age of 17 already stay in their parents' room for free. It's only the "play" portion of the "Play & Stay" promotion that could be considered an incentive.