Apart from two further Hreidarsson efforts, lacklustre Charlton never seriously threatened an equaliser and Palace's new-look defence held firm.
Humiliation at the hands of their south London neighbours was all too much for a section of the Charlton crowd who waited behind after the final whistle to jeer their team from the field.
Manager Alan Curbishley said: "I can understand their frustration, they have showed it a couple of times before.
"It was a big game for them and they were disappointed that we were beaten. They wanted us to win, let's hope we can make up for it against Middlesbrough on Saturday."
While Curbishley is poised to ring the changes in a bid to break a run of four defeats, Dowie faces a more welcome selection headache for Saturday's trip to Birmingham.
He said: "One or two people have made me raise an eyebrow. That will give me a selection problem for the rest of the games.
"We need 22 or 23 players pulling in the right direction and you don't do that unless you give them a reward at the end. We have got a squad which is capable of competing against Premiership opposition."
Following a tireless display and a well-taken goal, striker Freedman looks certain to have played his way into contention for Palace's Premiership team.
He said: "They had their full Premiership side out, but we have got a strong squad at our club. We have 22 or 23 players who the manager can call on at any stage. He knows everybody wants to play and maybe this was a little reminder."
Dowie is hopeful Andy Johnson will recover from a knee injury in time to take on former club, but Fitz Hall (knee) and Michael Hughes (hamstring) face late fitness tests.
