My children are 8 and 10 and love
Disneyland! I know some WDW visitors have some negative thoughts on Disneyland and my advice is to ignore them. That's what I do. Look at this way, you will have all the magic WDW offers with just enough differences to feel like you are trying something new. There have been many WDW regulars who have posted on this side of the dis who have had marvelous times at Disneyland, I wish I knew how to post links for some of those. We have been to WDW 3 times and are now DVC and we truly love it there but we also love Disneyland every bit as much if not a tad more. The "Walt" factor and the compact size and climate give it a lot of points for my family. I just love going to either coast to visit Disney and don't fall into the comparision mode too much. The Grand Californian is supposed to be incredible (we usually stay at the Disneyland Hotel but hope to try GC someday). As convenient as the Poly is to MK the GC is even more so to Disneyland and DCA. Steps from everything, including DTD. If you are planning on going this February you will have all the benefits of the 50th celebration without the crowds, although that may be around Presidents's week. Pres. Week in Disneyland however is not as crowded as WDW because I don't think the schools in CA have as much time off as the New England schools do. Also, I don't believe there are any cheerleading groups who go to Disneyland, we had some of that at WDW last Feb. and it made the crowd factor go up big time.
As far as weather, the best trip to Disneyland we ever had was in February of 2004. Perfect weather and crowds, we stayed 6 full days that trip and weren't ready to leave. We did mostly crop pants and light weight jackets for me and my daughter and my son and husband always wore shorts in the day and changed into pants for the evenings. Last January/Feb we went to WDW and froze! I have never been that cold in Disneyland in February or December for that matter. Like WDW, they keep the pools nice and warm so you can swim and enjoy your resort's pools in the winter.
If your kids love MK the most at WDW then they will not be disappointed at Disneyland. Disneyland has a better Fantasyland than MK plus has Indiana Jones which they will love (especially if they love Dinosaur at AK). DCA has TOT, Soarin and California Screamin which is my kids favorite coaster even over RNRC since its longer and has a couple of big hills. And you can park hop multiple times each day. Also, DCA has the Electric Parade on weekends that time of year so you won't have Spectro withdrawl! The thing that most WDW vets seem to miss is the fine dining choices and Epcot. However, Disneyland has our favorite character meal anywhere, Goofy's Kitchen located in the Disneyland Hotel which is about a 5-10 minute walk from the GC (think Chef Mickey's). I know that with the age of our kids (so close to yours) one or two character meals (which DL certainly has) and some decent burgers, pizza and chicken nuggets and they are satisfied! And while my kids enjoy Epcot they have more fun at Disneyland/MK and DCA/MGM. Also, the GC has Napa Rose which is the top restaurant in Orange County, CA if you want fine dining and DTD is right there and that offers a lot of varied, high quality dining.
If your kids are excited, I say go for it! I think it is every Disney fan's moral obligation to go to Disneyland at least once and during the 50th is the perfect time to try it out! Good luck with your planning!