That is correct. There are also park hour times guides at the resorts and park entrances and you can see all the park hours on there too. The Disney 'week' runs from a Sunday to a Sunday so your resort reception area usually puts the new week's guides out on a Saturday night
Morning Magic Hours you don't need your room key to go onto any rides as they check this at the gate when you enter the park (evening EMH already has a park full of mixed onsite and offsite guests and they do therefore check resort ID's for rides and shows).
They will check ALL guests' resort IDs including small children so make sure you keep them all handy. If they are using the wristband system when you get there, that makes it easier, assuming you opt to wear them on your wrist. If not, have them on a lanyard or somewhere easily accessible.
Have fun. We love EMH