McLachlan, fresh from a pro tournament in Florida, where he was runner-up in singles and winner in doubles, contributed two wins and allowed his team-mates to play lower in the order.
Otago's Paddy Ou lost 3-6, 2-6 to McLachlan but contributed his share to a competitive, entertaining match, while Carlos Reid was powerful and intimidating in beating former touring pro Perry Crockett 6-4, 6-3.
It was a shell-shocked Crockett who meekly gave up the last eight points.
The young Lakes players Miki Nobuzawa and James Smith beat Ryan Eggers and Mitchell Sizemore in straight sets but Eggers showed some fine touches.
Hume gradually worked her way back into the match and was close to pushing for a third set, but her lack of recent match play showed, while Price, who also beat Otago Open titleholder Rebecca Dellaway on Saturday, was athletic and focused.
Jessie Stevenson played well in the tight spots to beat Li Ying Moroney 7-5, 7-5 and Abby Edwards (14), on debut, did likewise to beat Tammy Smith 7-5, 6-4.
Anabelle Ecroyd had chances, and led in the third set but lost it 4-6 against South Island schools' champion Ines Stephani.
While the doubles were halved and the tie went down to a third set tiebreak, Lakes were able to hold on for the close win.
The return round will be held later in the season in Dunedin.
On Saturday, Otago beat North Otago 10-2 with Dellaway contributing twice in her team's loss by beating Hume and partnering an aggressive Nicki Wallace in doubles.
The Otago men kept a clean sheet, while Lakes won all 12 against North Otago.
