The Lagoon Tower is probably best for families because the most kid-friendly pools are located there.
I think that the Gold Lounge is now in the Palace Tower, which is in between the Lagoon and Ocean towers (but closer to the Ocean Tower) along a "horseshoe" shaped walkway (covered), and can also be reached via the various paths or tram/boat. With little kids it will probably be about a 10 to 15 minute walk between the Lagoon and Palace Towers. You may be better off buying fruits, juices, and cereals and eating breakfast in your room as opposed to the limited menu in the Gold Lounge.
I think a lot of people like the Ocean Tower because there are more rooms there with ocean views, and the Diamond Lounge is there.
I have not seen the size of the rooms in the Lagoon Tower, but I don't think you will have a problem with 2 adults and 3 little ones in a room. I think the rooms are probably average size, but you will should be spending most of your time outside anyway.