Have you been to any other Disney Resort (e.g., Disney World) before? If you've been to WDW, I highly recommend checking out
HydroGuy's A DLR Guide for WDW Vets.
In terms of planning...some basic questions...
1. Where do you want to stay? There are on-site options and off-site options. Each have their benefits and drawbacks. The biggest perk of staying on-site is access to Extra Magic Hour, which allows you into one of the parks an hour earlier each day (usually DL has EMH on Tue, Thu, and Sat and DCA has EMH on Sun, Mon, Wed, and Fri). The biggest drawback to on-site hotels is the cost. There are also good neighbor hotels nearby, which tend to be cheaper, but are usually "motels". There are some nice hotels over by the Convention Center, but they might be further than you want to walk.
2. How many days do you want to spend in the parks? The maximum length ticket is 5-days; after that you'll need to look into the annual passes. Personally, I think the minimum number of days you need to get a sense of the parks is three days. If you have more time, I would recommend 5-days (or as many as you can!). I would highly recommend getting a park hoppers because the two parks are only 110 yards apart (you can see into one park from the other park).
3. Do you like to eat at table service locations? Dining reservations open up about 60-days in advance (the system doesn't always release the dining reservations right at the 60-day mark, so if you try at the 60-day mark and something shows as unavailable, it's more likely they haven't loaded it into the system yet rather than already being booked solid). You can often get pretty good dining reservation with only a few days to go, but I do recommend making a reservation for a TS location if you have a specific location and/or time you want to eat. Otherwise, DLR has a lot of really good counter service (CS) options.
Other notes/thoughts...
- DLR generally releases their operating calendar about 45-days/6-weeks in advance, but the entertainment/refurbishment/etc. information is not always complete at that point. That information may be added later (closer to the 30-day mark).
- If you aren't already familiar with Fastpass, I would read up about it. Also, given the ages of your children, I would look into Rider Swap if the parents (and older kids) want to do any of the "thrill" rides (e.g., attractions with height requirements).
- Baby Care Centers are awesome for infants and toddlers. There is one in each park and it includes a semi-private place to nurse, fairly nice changing stations, a training potty (closer to the ground and without the auto-flush sensor), and a place to warm milk bottles or toddler/baby food.
You'll be there during
Bats Day in the Park (4/29-5/1),
Spring Dapper Days (5/1), and part of the
Tinkerbell Half Marathon (5/5-5/8). Of those, you'll mostly likely notice an uptick in crowds during the marathon period and will mean some road closures (if you're driving).