At ages 7 and 9 your children will more or less grow up with Eddie, which will be wonderful for all three of them.
bronco's tip number 2 is ^. Dogs are so much different than cats, and once Eddie knows that you / your husband are the alpha dogs, as it were, things will go smoothly. And they do love exercise, bless 'em.
The cats will probably raise a collective eyebrow and say 'oh, really?' and deal with the dog in a feline way. Although they're not good with change, they'll get used to having another creature around.
Animals have huge hearts, and give soooo much. Love him and he'll love you back without restrictions.
Welcome to FT, Eddie! Good dog :-: