My hubby and I just got back from doing the same. We try to go annually kidless too. Like the others have said, research online before you go. Know which attractions you really can't miss. I would suggest doing each "land" completely before moving on. This saves the feet. Once you have experienced all the lands, go back and repeat. If you use the fast passes, while you are waiting for your time to return, visit a neighbor land so you don't have to walk too far. You will want to see Fantasmic! It is great. You will notice that people camp out around the Rivers of America for several hours before it starts. Keep riding. Go and ask those in the seated areas if there is space for the 2 of you. Or better yet, if there is a second showing, see the fireworks first and then head over for Fantasmic! Do see the fireworks too. I love this fireworks show. Ask a castmember where they suggest viewing from. People camp out for the best viewing spots for this one too. If your feet are tired, consider camping out yourself.
California Adventure is fun too, but we can do it all in less than one day. There are parts that are currently going through a make-over, but it doesn't stop the fun. If you're a HSM fan as I am, watch the HSM3 parade. The Aladdin show is fabulous! The Animation area is great too.
In both parks, look at everything before you decided to skip it. We have had great times in lesser attended attractions. We were glad to not have missed them.
Window shop all the stores first. Maybe use a note pad to write down what you found in what area. Wait until the last day to make your purchases. You don't want to have to carry them around.
There is also a Disney warehouse about 4 miles or so due North of the parks. If you go to ams-liquidation.com, you can get direcions to the Fullerton store. They have previous/old park merchandise and discounted prices. Last time they also had discounted park tickets. We always go there too and usually buy the kids souvenirs there. We can usually get shirts for all 4 kids for under $50.
I can go on and on. I really love Disneyland! I have been too many times to count. We love to take the kids, but we really love to go alone. We spend 4 days in both parks without being bored.
Have fun! I wish I was going again.