Buying one-way cash tickets to or from the USA can cost nearly as much as a round trip. And finding 5 passengers of awards will be challenging. So my advice is to use points for as many r/t as you can and buy the other tickets cash. Or at least price up a one-way before booking one-way on points! Remember that if yours is cash it will be a bunch of MQM and MQD towards next year's status!
If you have one of the DL Amex cards there's also Pay With Miles at a fixed $0.01/skymile, but they go towards medallion status too and might be necessary if award flights aren't available for all 5.