Anyways, it probably would have been much easier to contrive some reason why your squad mates had to go back to the Normandy just after that wave combat sequence with all the banshees and prior to the beam run itself.
There is an easier way.
Steve takes Shepard to London, and a few moments later, the shuttle takes damage which either leads to Steve being killed or lives, if Shepard talks to him throughout the game. The other shuttle is used to take the other squadmates to the forward operating base. If Steve survives, he's able to crash land the shuttle near the fob. He gets there with only a few bumps and bruises. He mentions that he was lucky no uglies were in the area the shuttle crashed. This gives him a goodbye with Shepard in person.
When Harbinger fires his beam at Shepard and squad, Shepard is injured as seen in the game, and because the squadmates were behind Shepard, both suffer minor injuries. Steve sees that Harbinger flies away and gets in the other shuttle, along with the other squadmates and heads to the beam. As the squadmates head to the shuttle, they turn around long enough to see Shepard go up the beam with Anderson right behind her/him. Of course if Steve is dead, someone else can take the shuttle to the beam to pickup the squadmates.
I included Steve because there is no explanation of how he ended up back on the Normandy. Not sure if he was on the Normandy when Shepard talks to him during his holobye.