We went in January 2012 when DD was 4.5yo. She was still at nursery (we're in Scotland) so I was able to whip her out for a Monday-Friday break before she started school. It was cheap as chips because of the time of year and we just had the best wee holiday. It really was fab.
We stayed in the Hotel Santa Fe. It was basic but clean and the room was big with 2 double beds. You really don't spend much time in the room, so my advice if you're on a budget is to not bother wasting money on a more expensive hotel. You're literally there to shower and sleep. We paid for a meal plan which was definitely worth it as the food is very expensive in the park restaurants. We really filled up at breakfast to see us through and we cheekily snatched some fruit away with us to snack on during the day. Our meal vouchers meant that we could eat at various different restaurants, so we did Planet Hollywood, Cafe Mickey and the Rainforest Cafe. If we ever had a difference to pay and make up, it was fairly small. Cafe Mickey was fab for DD as there were loads of characters walking around - they would all stop for autographs and pictures. She got lots of high fives 
Again, because of the quiet time of year we just made restaurant reservations at the hotel desk the night before we wanted to eat. Got in no problem. The only gripe I ever had in the restaurants was in Cafe Mickey. I had a tiny difference to pay on top of my vouchers (think DD had needed an extra drink), so I put down a 20 Euro note as I didn't have any coins and the waiter didn't bring my change back. Think is was about 15 Euros. When I asked about it he made a huge fuss about it being his tip and how those of us using meal plan vouchers never tipped well 
I was adamant about wanting my change back, which he brought me in dregs as he felt he still had the right to decide how much of a tip I would leave him. I eventually had to get the manager involved. The worst of it was I would have happily left him a decent tip if he hadn't been such an arse!
Free buses to the parks run regularly from the Disney hotels and they don't take long. There is something for everyone in the parks and your kids will thoroughly enjoy themselves. My DD isn't a fan of any 'thrill' rides but there were loads of gentler ones to keep her entertained. Because we went midweek in January we were just walking onto things without queuing - it was bloody brilliant. Make sure you go and see the parades and make full use of the additional park hours if you get them. We spent two full days in the Disneyland Park and one day at the WD Studios.
Prices in the park are extortionate. I bought some Disney Princess outfits from my local Tesco and took them with us. I'm glad I did - the dresses in the park were an eye watering amount. I gave DD some pocket money at the beginning of the week and made it clear that it was her money to spend as she liked, but that was it. This avoided any whining or arguments, not that she's ever been a grabby I-want-I-want-I-want child, but it's Disneyland and everything's so sparkly and enticing for them. I'm glad I had the forethought to do this as it meant she adopted a Gollum-like attitude to her precious money and she was very careful about her spending. God love her, she wandered around the shops looking at everything and calculating how best to make it stretch 
She treated herself to some Minnie Mouse figures and some mouse ears - puffed her chest out the whole day having bought them 'herself'
We're heading back at the beginning of December, doing Friday - Monday. We were initially supposed to go in February while her school was on holiday, but with all the problems in Paris just before that, I got nervous and moved the dates. Same as before - Santa Fe, meal plan and lots of fun to be had. Hopefully it'll be a lovely start to the festive period!