We have two sons, now both grown, so I understand what you mean about wanting space for your boys. I can't really answer from any personal experience, but I think you have to make that old "Pros and Cons" list. Put it down on paper. When I do that, the answers often jump right out at me.
It looks like you have a lot of area left, but I can't tell for sure. If you added deck, how much yard would be left? How often do your fellas play outside? And what do they like to do when playing outside? What is your family into? Such as, are ya'll a big soccer family and need lots of space to practice? Our boys (13 months apart) were so into competitive swimming from ages 5-18 that they were hardly ever home (a regret looking back). You didn't mention their ages, but if old enough, what do they have to say about keeping/losing more yard? Of course, you and your wife are the adults and must make the final decision, but sometimes kids can zoom right to the heart of a matter (out of the mouths of babes). Young ones often give the most honest and pure insights.
I guess my vote, since ya'll are wavering, would be to wait. You can always add more decking later, but it's much more difficult to remove it (I think, or maybe not?). Keep in mind, saving a buck is usually tops on my list, but also, I like to take my time with decisions (like waiting to get a pool when retired - Ha Ha - maybe that was a little too long).
Either way you go, it will still be gorgeous! Good luck deciding, and let us know - with pictures! Suz
