I feel guilty for changing Jobs while the staff goes on a business trip

Some Context: Working for my friend’s mother’s small business for 6-7 years now.

I currently work there as a graphic designer, but they also gave me other responsibilities such as: Helping out at their warehouse lifting boxes. Unloading containers (not as much since covid). Taking orders on the phone and in-store. Taking dropshipping orders. Handling dropshipping returns. Helping with installation jobs. So basically I’m doing a bit of everything.

The reason I’m looking for a new job: Looking for a pure graphic design role. Currently, I get paid $2,000 which is pretty low for my job scope and I would like to get paid biweekly, they pay me once a month.

I don’t get paid overtime even though I have worked overtime hours. I have no benefits.

Recently they have been planning to go on a business trip for a week with the Daughter (friend), Mother and a Manager. But at the same time, I have been looking and applying for jobs casually.

Fortunately, I have found a job, however, the starting date is three days before they come back. And there is only one other person to work for those three days alone in the front office.

I brought up that I will be resigning which they are okay with. But they keep telling me, I should’ve let them know ahead of time if I was looking for a new job as it was disrespectful. Especially, when I knew they were going on a trip and the other coworker would be alone.

However, I didn’t expect I would get a job. Also, in my opinion, I don’t think it would be a good idea to let your employer know that you’re looking for a new job. Because it’s not guaranteed I would get one.

I forgot to mention, they would also like me to come back (after I get my new job) to train their new hires, because they don’t know how to run the websites and other things. Because we are ‘family’ and we should help each other.