There aren't really many lakes in the Tri-cities area besides the family fishing pond.
The Family fishing pond in Columbia park is perfect for kids (14 and under, or 65 and older), its usually packed down there after the lake is stocked, but i have no idea how it is right now since im too old to go now, but the fish they put in there are huge.
The best place to fish down there is between a bridge and a fishing dock on the south side of the lake, hit it early in the morning with powerbait, before the crowd comes!
The other option is Dalton lake, which is over in Franklin county...