Generally August is a busy month as schools throughout Europe are on holiday. However, don't let this put you off. During this time of year DLP has is extended summer opening hours (9am-11pm at the
Disneyland park, 9am-8pm at the Walt Disney Studios), you have the best chance of fine weather and the parks will have their full roster of parades, fireworks and entertainment. A mid-week visit in the summer is my favourite time to visit DLP.
If you are staying in central Paris it is perfectly possible to take a day visit to DLP. You can reach the resort by train, taking 45-60 minutes depending on your kocation in the city. But I would recommend you make a slightly longer visit if you can afford the time. The Disneyland park in Paris is, in many people's opinion, the best of all the Magic Kingdoms around the world. It was recently described by Kevin Yee on miceage.com like this: "this first French park is a masterpiece. Lead Imagineer Tony Baxter masterfully distilled the essence of Walts Disneyland, refined the thematic elements, and reconfigured the layout for maximum effect. Jaw-droppingly beautiful and stunningly executed, the park is just gorgeous." I whole heartedly agree with this, so while a one-day visit would allow you to see Disneyland's headline attractions, I think another day or two would give you the time to absorb much more of this beautiful park. There's also a brand new theme park at the DLP resort, the Walt Disney Studios, which although still small has some unique attractions which are of the highest quality.
I've never been able to find a source for discounted tickets at DLP, unfortunately!
Regards
Rob