Mixture of newly replaced boards and old

I live in Maryland and until today we were planning on painting our 20+ year old deck with the Olympic restore paint. Thanks to this site we decided not to continue with that plan. However, we have replaced quite a few boards on the deck. So now we have new pressure treated pine on about 35% and the rest is previously stained from when we did it about 10 years ago. So far we have power washed the whole thing. The deck is mostly southern exposure with some on west and east side as it wraps around the sunroom of our home. Do we need to wait until the new wood is cured and then proceed with staining the whole thing. What product would you suggest. Should we replace the rest of the boards? Just not sure how it will look with new wood and old wood with stain. No mold or mildew.