Well there are many different levels to this question. First of all - Disneyland and Disney World are pretty different in the way you’d spend your time. I’m not sure where you’d be coming from, but flights/driving would probably be your first concern. But in combination with that- Disneyland is smaller size wise and there are less individual parks to visit. It’s been a long time since I’ve been to Disneyland, but I think you could pretty much get everything done in 1 day if you just went there and maybe 2 if you also wanted to do California Adventure. Disney World is much larger and has 4 different parks, 2 water parks, and other places to walk around like Disney Springs and the Boardwalk. Many people come to WDW for a week or longer. Basically- if you want a short trip Disneyland is probably the better bet, but if it’s cheaper to get to WDW, it’s possible to make it short, you just wouldn’t see or do everything.

As far as groups go- I know there are probably some discounts, but I’d recommend going through an agent. Many Disney specific agents are free and they can give you some quotes. Here’s an example-

https://www.smallworldvacations.com

As far as your family goes- the above agent could help you there too, but I wouldn’t expect giant discounts. While things are often advertised as “discounts” they are by no means cheap. We visit WDW frequently and throughout the year they’ll offer room and ticket packages and sometimes they’ll offer something called free dining. These things may save you a little bit here and there, but in the end, it’s still very expensive. If you work with an agent they’ll look for the best deals and then they’ll usually monitor for changes to see if you can get a better deal before you go. Disney is definitely something you budget for, though. I’ve never heard someone brag about the great deal they got. Some times of the year or hotels are cheaper than others, but the total cost is still pretty high- just keep that in mind!