Crusaders opened the scoring midway through the opening half thanks to Stewart.
Ross Clarke swung a corner in from the near side and Stewart headed the ball up and over the reach of goalkeeper Max Little.
The visitors doubled their lead eight minutes later as defender Cameron Stewart under hit his pass back to Little, allowing the alert Offord to nip in, round the goalkeeper and roll the ball into an empty net.
It could have been worse for the Bannsiders as Jimmy Callacher rattled the woodwork on the stroke of half-time.
Coleraine, too, had their chances in an end-to-end first half, Shevlin and Rhyss Campbell both hitting the crossbar from headers.
Shevlin did throw the hosts a lifeline 15 minutes from the end, heading home Dean Jarvis’ cross from the left from close range for his 13th league goal of the season.
But their hopes of finding an equaliser were dealt a blow as McClelland was shown a second yellow card by referee Declan Hassan minutes later after tangling with Offord.
Johnny Tuffey denied Coleraine a late equaliser when he turned away substitute Kyle Spence’s fierce angled drive as the Crues recorded a third successive 2-1 win over Dean Shiels’ side.