Just realized I forgot to post pics so I will include them below.

Here is a link that might be useful: House pics

That's apparently a bad link (the "h" of the "http" is missing).

Hopefully this link will work

Here is a link that might be useful: House pics

I would put stairs leading down from the deck towards where you have the doors on the corner and a small patio for sitting in front of those doorshalf way down I would have a landing and cut a small patio into the hillside to house your hot tub. Then it would be accessable from the patio or deck.

You could build a pergola over the hot tub and plant vines to climb up the pergola. This would involve a small retaining wall. Then I would have plantings going off from the hot tub patio around the deck, with tall shrubs in back to hide most of the underside of the deck.

I think digging under the deck to provide a room might involve structural problems

It seems like you will need some on-site professional advice. I'm no where near that, so can just add some reactions. Your home appears large and a large financial investment, so you want to keep things appropriate for the setting and not tacked on here and there.

The low level by the basement is not very easy to "connect" well with the high deck so as to have the 2 spaces function really well together. The other side yard that is a higher elevation seems the most natural area for spillover from a large gathering and I would be tempted to develop that space preferentially, even if it requires some privacy screening from the front view of the property. However, if the basement room--whatever you will be making that in to--is a key action zone that will be highly related to outdoor activities, then maybe you do want to develop that walkout area more.

A hot tub under that deck doesn't seem very appealing.

So, to come up with the best design, you may need to flesh out your activities and traffic flow a bit more to see what is most rational from that standpoint and then factor in the $$ cost of various solutions. Also prioritize--you are trying to do this--decide if pleasant seating out of the rain is most impt, or heating in cool but clear weather, or being in hot tub, etc.

I'm not sure you can build a fireplace on the deck proper, if that's what you meant.

You're lucky to have such a beautiful setting and such a plenitude of possible locations for entertaining and recreating.

Some ideas:

Consider painting the concrete foundation to match the red of the brickwork.

If the deck faces south or west, you might want to plant a couple of shade trees. It'll be a few years until you get much benefit, but when that time comes, you'll be glad of the shade. (And do price larger trees to see if it's worth your while to save a few years of waiting.)

Another option for using the area under the deck is as a storage space -- a bit more difficult to retrofit than if you'd planned it from the beginning, but probably still possible. I have some under-deck storage (I use it for firewood); the previous owner kept his riding lawnmower there. At one point I was considering walling it in with lattice; your layout lends itself to better-looking possibilities than I have figured out for my situation....

Consult a professional landscape designer.
Your back yard is severly sloped and you have that giant concrete on the side of the house.
There are going to be grading and drainage issues that a pro will need to know when they come out to your yard and inspect it.
You have a beautiful home. You really should have a pro make your outdoor living space as beautiful.
Good Luck! and post a pic of the finished product!

I thank you all for your input. I think we are going to be best serve by spending a few hundred dollars and having a local professional come and see the site and give us input and design ideas.

Kristen