As it stands right now, we're dealing with the fact that when John and Elly have to be away from the house for an extended period of time, the two of them exploit Annie shamelessly while offering her not much in return. This persisted up until, oh, about a year or so after April came into the picture and Annie became A Bad Person To Be Around because stupid Elly stupidly misinterpreted what was happening in the woman's life for the longest damned time. This meant that when it came time for the 1995 vacation of getting away from April, they did what they did in the eighties and parachuted in John's folks. The upshot of that is that not only was April unsubtly given the message "Your mom and dad don't want you around because you're naughty and unwelcome and they're stupid", she reacted to being lied to by having her own boat trip of slipping into a river and damned near dying because Elly is too stupid to buy a real lock for the gate. Since Will and Carrie's 'magic' wasn't strong enough to protect the offsprings, they'd hit on the idea of dropping them off at the Enjos and Maguires up until Lizzie was at an age wherein someone unwelcome might come to talk her into doing something she's not ready for. (By someone, I mean Anthony and by something, I mean going to second base.)
The problem of what to do with the kids became a real problem once Liz went off to college to be tainted by Eric and thus spend years in purgatory until she became worthy to spend a bland non-existence with a dullard. The solution hit on was to keep April out of the mischief Elly was sure she would get into by forcing her to spend her afternoons as Elly's flunky at the bookstore. Since it was Mike's stupid idea to keep her from having the same freedom he envied because girls need policing, we add being a rock-ribbed God-damned Neanderthal to the list of charges against him.