Last Minute Trip - need advise

Just found out that I will be going to Bangkok in two weeks, connecting via Tokyo. So, I decided to stop for a short trip to TDL. I am arriving in Tokyo on a Saturday around 2:15pm. I'm assuming I can get to my hotel (Hilton Tokyo Bay), check in and get tickets and be at TDL by 5:00. That will give me about 5 hours – first question, will that give me time to actually do anything or will it be so busy that I won't get to do much?
I'm planning on spending Sunday at TDS and then my flight is on Monday at 3pm, so I was thinking since the park opens at 9 on Monday I was hoping to spend about 2 hours at TDL and perhaps hit Monsters, since I doubt I'll make that on Saturday.

Does this sound like a good idea or should I do TDS on Sat and TDL on Sun?

I don't see anything about extra magic hours so I assume they do not have any?

Any other suggestions you can offer?

It won't matter which park you do on Saturday, they both are going to be extremely busy. The weekends are the busiest times for both parks. The time you arrive on Saturday most Fast Passes will probably be gone. I found it works out best to do some of the more popular attractions an hour before the park closing, then they are almost walk on or very minimal wait. This goes for both parks.

Going Monday morning you should be good if you're there right at park open. They do have some "early" entrance but it's something like 15 mins before the park opens, nothing special.

I hope this helps :) Disneyland and DisneySea are both fun parks and you'll really enjoy it!