I am nervous to put in my two week notice: Advice?

Hello everyone, I recently (3 weeks ago) returned to my job after maternity leave, and am now wanting to turn in my resignation notice for a variety of reasons- wanting more time with my kids, wanting to seek training or education for a higher paying job, and unhappiness about the way situations are handled by higher management. However, after 4 1/2 months of maternity leave and knowing that our busiest time of year is coming up, I feel very guilty leaving and am having a hard time working up the nerve to put in my notice. I am willing to stay until they hire a replacement, as long as it’s within a reasonable time period. Has anyone else resigned so soon after maternity leave? Advise and support would be much appreciated!