Wouldn't take them to a women's match for their first (and possibly last) visit to Goodison. See who we draw in the early rounds of the FA Cup and if it's a lower division team you'll get three together and at a cheap price.
They usually stand all match in the LG so that's no good for kids of your age. Upper would be alright, or Family Enclosure or Paddock. If they like spending time with old people then the Park End is the place to be.
There's no better feeling than when you take them for the first time, walking up the steps from the concourse and seeing the look of amazement on their little faces when they see the pitch and the ground from the inside having seen it on the telly.
If you're travelling from far afield and staying for any length of time it's well worth looking into going to Finch Farm and waiting outside for photos with the players as they leave, nearly all of them will stop for a pic when they see kids waiting.