Hi Reka,
It sounds like you're going to have a lot of fun with a large group visiting Walt Disney World!
I suggest that you visit Magic Kingdom Park. It is classic and is often what people think of when they think of Disney. There are so many attractions at Magic Kingdom Park that would appeal to the range of ages you are traveling with.
I recommend that you be willing to split up for at least part of the day. That way, the 8-year-old can experience some of the more thrilling rides, and if necessary the 2-year-old can it easy for a while in the mid-afternoon. When we travel with large groups, we like arriving together at park opening time and riding one or two attractions together first. After that, you can split up for a while in the morning and then meet for lunch. After lunch, you can split up again for a while and then all meet back together to watch the afternoon parade.
Attractions that your whole group may enjoy together include Jungle Cruise, Mickey's PhilharMagic, and the Tomorrowland Transit Authority PeopleMover. The younger ones might enjoy Dumbo the Flying Elephant and Prince Charming Regal Carrousel. The older ones might enjoy Big Thunder Mountain Railroad (40" height requirement), Splash Mountain (40" height requirement) and Space Mountain (44" height requirement).
Those are just suggestions - there is so much to see and do at Magic Kingdom Park! I recommend that both you and your friends take advantage of the
free customized maps of Walt Disney World Parks. This way, your children (or parents for the younger ones) can explore the attractions that are most interesting to them, place them on customized park maps, and have the maps delivered to your house before you go!
Have a wonderful time visiting Walt Disney World, Reka. Please do not hesitate to ask if you have any further questions!