with our akita, when he was growing up he was very pushy. if he wanted to play with another dog, he would NOT take no for an answer, and would instigate until either the dog gave in and played or it started a fight. he is very friendly, BUT, he can be super duper unfriendly if he doesn't like you for whatever reason. he was very well socialized (every day we went out to meet new people!) but he still picks a few people he doesn't like and he will not tolerate them. at all. strangers alone in your yard? forget it.
as for kids, i have two sons (1 and 3) and he absolutely LOVES them and will take anything they can dish out at him, but he is only 4 months older than my oldest also so he grew up with them. if you well socialize them with kids, they are awesome family dogs. the problem, they can be very protective of the families' kids, even towards their friends if they are too rambunctious, or if they start to "play wrestle" or something. my 4 year old akita will pull my husband away from me by the arm if we're playing too rough for his liking. on a side note to that though, with us my akita and i have a very special bond, and have been through a LOT together where as my husband has been deployed more than home regardless of the fact we've been married longer than i've had axle.
since you mentioned that your shiba is older, you may want to think about any health problems he has, esp. arthritis or HD. akita's are infamous for "stepping" or "stomping" dogs when they're playing and since they are a big puppy it can cause problems for dogs who already have senior related problems.
overall, if they get great training from puppy-hood (they're very stubborn dogs) they can be GREAT pets! they're extremely smart, sometimes too smart for their own good! be prepared for a ton of shedding, and make sure you research your breeder. axle came from a BYB and is in awful physical condition, cross eyed with HD, and skin probs. if you do get one, please post pictures! i miss seeing axle as a puppy, and our akita / chow mix i never got the chance to see her small!
here's a pic of axle at 3 months of age and one now. here are his stats, he is bigger than the AKC standard though.
32" at the shoulder
140lbs
4 years old