Alternatively consider buying economy tickets for you all and paying for all of you to go into the Plaza Premium lounge at T5. I suspect that might be cheaper than buying 2 Club and 4 Euro Traveller tickets.
That only solves the lounge access at LHR and not in Stockholm on the return but if it is that important to have lounge access for the return you could also consider Priority Pass which will get you lounge access in there.