As long as the chicks are protected from wind and cold drafts and rain from soaking them, they should be fine. As for the placement of the heat lamp, watch the chicks. If they don't spend any time under it, it may need to be raised. A thermometer placed directly under the lamp will tell you how hot it is on the ground where the chicks are. It should read between 85F and 90F the first week.
Jen is right about the peeping. Day and night is a desirable thing for baby chicks to allow them to sleep at night and establish those important rhythms. It's hard to do this with a heat lamp. I used to block the light at night with a dark cloth when I brooded indoors, but doing that outdoors risks a breeze blowing the cloth against the hot bulb and starting a fire.
What was the reason you nixed the heating pad? It's ideal for outdoor brooding. If you tell us, maybe we can help solve the problems you are having with it.