Personally, I prefer a trellis to be just about as tall as the vine is expected to grow. It depends on what you like... and what the vine is willing to do. I've seen lovely roses that were a couple stems for the bottom three feet, and then a mass of bloom upwards; and I've seen climbing roses clinging to the top of a fence for 10 or 15 feet. I have clematis that grows to 4 feet and other clematis vines that grow from 6' (in trellis) to 12' (those tall ones are happy covering an arbor). OTOH, ivy will often grow 20+ feet and requires pruning in an attempt to keep it within shorter bounds. Sketch your ideas out, and find out if there is something special your son would like to have. (Sorry, redwood trees don't grow well in Virginia, but a red wood playhouse might appeal.) If you can work something just for him into the plan as well as having him help plant and care for the new stuff, I suspect you both will enjoy the yard more.

Other people may use landscape specific programs to create mock-up pictures. I'm using Microsoft Paint. I like it because it is simple but versatile. If one knows the basic elements of drawing and painting, one can accomplish the same things one can accomplish with papers, pencils, brushes and paint ... and more because it has the cut and paste feature. While it is on many computers, one cannot use it very well unless one has touchscreen capabilities and a stylus. Yet without that, many of the features will be useful. All of the tools are well explained in the help menu. The cut and paste feature is what allows one to cut photos apart and reassemble their pieces as a panorama (if they are taken from the same camera viewpoint.) The picture can either be opened in the Paint program, or it can be grabbed off of the GardenWeb forum with the copy feature and pasted into the open Paint window. (Click on the picture first to copy the enlarged version instead of the shrunken version that shows on the forum.)

This is what wood lattice looks like: Wood lattice You would cut it to size to the same size as the three faces of the porch roof and possibly mount it set-off from the porch itself by the thickness of a 2X4. Think of it as a horizontal trellis wrapping around the three sides of the porch roof. If you enclosed the columns in the same lattice, it would look more integrated. Then you would plant vines in the ground and have them grow up the columns and along the top edge of the porch. If you don't like that, there are all kinds of designs you could go with using some horizontal 2X2's to add more interest to that plain porch edge. You could also mount trellis or lattice work to the two sides of the porch to give it a more interesting look.

Question - are the curio/bookcases under the loft area two units? If so, i think separating them and putting them where the ceiling is higher. Possibly put that buffet where the French curios are now where you could put a pair of lamps to help give warmer light to that area. The overhead recessed lights are harsh at best. Two of your chairs angled slightly toward each other with a lamp and table across from that area would create a nice reading area. A pair of other chairs could back up to that area and sofa facing TV. Big antlers on wall over sofa. Putting them over mantel makes for more brown on brown. You need some art there. What is size of mirror? I have a great chandelier installer that could handle moving that chandelier. There are tricks of the trade and equipment that can change that out with very little trouble. Takes some preplanning and depends on what you want to do with it, but might not cost what you fear. I have moved a very large Schonbek crystal chandelier, they made a wood crate for it, took down with pully system, put in crate and moved with some internal packing, put it in storage. When we were ready, they picked it up, brought it into our new home, lifted it out of crate and hung it. Not one crystal was lost or broken. The crate cost about $200 and the removal and rehanging another $275. So, it can be done, just depends on where you are and what your priorities are. Don’t make assumptions. Get estimates and talk to several area experienced providers. They will know.