You should be fine as long as you're careful....
Keep the HPS 2-3 ft from seedlings.... as a rule of thumb - place your hand - palm
down - over the tops of the plants - if it becomes too hot for your hand - its too hot for the plants..
Once they start to take off - lower the lamp - 20-30 cms is about as close as you can go with aclimatised plants..
good luck..
Laz