IF you have booked via the virgin trains website then providing the service isnt busy you could facebook them and they would then ask for your booking ref numbers and seat you all together I have done this in the past
Virgin do seem to undo much of the good things they have acheived on the WCML by their odd seating system. Given that the choice of "good" seats is limited on the Pendolinos, it makes selecting a seat at booking all the more important. I dont do facebook and if I did, what a faf to simply get seats allocated together. Airlines achive this without difficulty.
A shame really as the service I generally use from London to Manchester is fast and frequent and has an huge amount to recommend. For example, I let a very busy train go this afternoon, knowing the next departure was a mere 20 minutes away. But seldom have I sat in the seat allocated by Virgin (usually near the toilet/looking at a pillar rather than a window/squeezed in with others when half the carriage is empty etc)!!