It does not depend on the load on the "crontab program" (cron) itself. You should look at metrics (cpu utilization, io rates, web query response times) during the time your job(s) are running - is there a noticeable spike? If the programs "don't take long", that's a good sign that it's not a problem.
Have you experienced issues in your system related to this? Do you want to run cronjobs related to your LAMP/MAMP/WAMP instance?
If you're still concerned, you can do other things to limit the load: run the jobs with nice to reduce their priority, run them sequentially instead of simultaneously, and so on.
I hope it helps