Paradise Lake is an excellent trip, though I don't know if I would recommend it for an out and back day trip. The hike out to the lake is moderate to difficult- only about 7.7 miles but very little of that is flat. The lake is a beautiful, lush, living lake. There are fish and the lake floor is mucky. There are a number of granite rock islands you can easily swim/walk to, and the scenery from the lake is gorgeous. There are some really nice places to camp right on the southwest shore of the lake.
You can get from Paradise lake to Warren lake, but the trip is difficult, especially carrying packs. It's a short distance but a giant descent, and includes mostly climbing/shimmying down broken rocks and following a confusing trail. I would do it again, but it's tough!
Finally, hiking on the Warren lake trail is very difficult! Going back from warren lake, it's difficult to find the trail that comes down to the lake and once you do, the trail starts out with an extremely steep mile long climb! After that, there are many more climbs and descents. I would not recommend doing that hike in one day unless you are carrying little or are VERY fit.