Hello there!
Welcome to planDisney! I was happy to see your question appear in the queue because I love photography as a hobby and one of my favorite things is to take my mirrorless Sony camera with a nice low light lens into the Parks and capture beautiful shots of the Disneyland Resort. Some of the best pictures I have of my kids have come from these trips.
I'm happy to report that you should be allowed to bring your camera and tripod into the Parks with you. As long as you are in compliance with Park Rules and Regulations, you should have no issue making it through the security checkpoint. As stated, tripods cannot extend beyond 6' and must be able to fit into a standard backpack. Another thing to note is that commercial photography is prohibited without permission from Disneyland representatives. However, if you are just doing your friends a favor to capture their magic moment, that will be fine. I might recommend refraining from bringing all your equipment for a professional photoshoot, though, because ultimately it will be at the discretion of the security Cast Member what goes through.
I also wanted to wish your friends a huge congratulations! Is this going to be a complete surprise for one of them? For another perspective, they could also take advantage of the Disney PhotoPass photographers that are usually located in front of Sleeping Beauty Castle! Afterwards, be sure that they sport some Complimentary "I'm Celebrating" Buttons that can be obtained from City Hall. I'm sure plenty of others will want to congratulate them as well! In fact, since you're there, it might be nice for them to have some nice engagement photos around the Parks! Since you've got the Castle covered, some other picturesque spots to consider would be:
- The arch between San Fransokyo Square and Radiator Springs Racers. I like this location early before crowds arrive but it's absolutely stunning at night when Ornament Valley is lit (you'll need a flash because it's pretty dark here).
- The platform at the World of Color viewing area with Pixar Pal-A-Round in the background. Especially nice at golden hour.
- In front of the lagoon at Finding Nemo Submarine Voyage. Bonus points if you catch the Monorail going by.
- For Star Wars fans, anything in front of the Millennium Falcon, but venture off to the side where it's less crowded.
- On the Fantasmic! stage at Tom Sawyer Island facing towards New Orleans Square. If you have a long enough lens, maybe you can even catch them from across the Rivers of America for a nice isolated shot on the stage!
I hope that gave you some more ideas. As you can tell, I love seeing the Parks through a lens and really enjoy the pictures that come as a result!
Thanks again for stopping by and I wish you and your friends my very best wishes! If you have any more questions, please feel free to stop by again because we'd love to hear from you again and you're always welcome at planDisney!
Wishing You a Great, Big, Beautiful Tomorrow!
-Al