To recap and add to what others said:
8 and 10 year old can ride everything with or without an adult except Autopia. This includes going through the single rider line, which children under 7 cannot do.
6 and 2 year olds must be accompanied by an adult on ALL rides, even if they meet the height requirement to ride. This means on Mater a parent would have to ride with both of them in the same vehicle (they fit an adult and 2 kids easily), the little kids cannot ride with your big kids because they must be with someone 14 and older at all times. Gadget’s go coaster could be a difficult one depending on CM you get. They allowed DD to sit in front of my husband who sat with our DS even though DD was not quite 5, but different CM could be more strict and not allow that. They will do a rider swap at the exit if you ask.
The 4 month old can ride any ride without a height requirement except Roger Rabbit (and maybe Lady Bug Boogie), which requires a child be able to sit up independently. We have taken an infant to
Disneyland and it’s not too bad. They’re pretty indifferent, but you’ll enjoy it. There are more rides without height requirements than with.
Don’t forget to take advantage of the Rider Swap. The rider swap will allow three people to ride again. You can use FP and Rider Swaps together to make it possible for a parent and all 3 big kids to re-ride a coaster ride after the other parent has ridden them. It’s a bit of a strategy, but not too hard to figure out. They will probably want to see your non-rider(s) when initially asking for the pass, but you don’t have to hang out at the ride after the rest of the group gets in the queue. If you’re waiting for them to get off of Space Mountain you can take the little ones on Buzz Lightyear or Astro Orbiters, or even over to Fantasyland, etc. Also, Rider Swap passes are good all day, they do not have a return window like FP and can be saved for any time that day. Unlike FP. You can be strategic about this if you like, though sometimes getting a large family from one area of the park to the other is more hassle than optimizing ride time is worth.