I've sorted out the nest undermining our drive with 2 Raid bait boxes - they're little plastic domes, about 3" across, with holes for the ants to get in and out to carry the poison back to their nests. I've put one at the main entrance to the nest, and another halfway along one of their favourite runs. No problem with my 3 year old - she asked what they were, I told her, and she understands that it would make her poorly if she touched them. We haven't seen a single ant for a few weeks now - 3 months ago they were burrowing under the block paving at the rate of about a foot a day. We could tell by the new piles of sand appearing in the middle of the drive!