I need a babysitter BUT ....

So today I was over at my mom's house, doing some laundry. I brought up that if she would mind babysitting on Valentine's Day. Me and my fiance rarely go out. We have two boys a toddler and a 5 month old. My sister shot back at me that I take advantage of my mom because I know she won't say no. Like I said, I don't know how I take advantage because I never ask. Just this once for Valentine's Day. So I said okay, I'll get a babysitter for that night then. My sister said "why get a babysitter, you can't trust strangers!" My mom said "you're going to have a stranger watch the kids?" I'm sitting there confused as hell because my sister just said I take advantage of using my mom as a sitter and my mom doesn't want to sit but they attacked me when I said I need a babysitter from the outside.

Then my sister said "why not just pay me to babysit" and my mom said "why don't I get paid?" She said "$20 for each kid" I said "Well I might as well stay home paying that much for a couple of hours I'm not going to have money for the date"(this was a joke BTW). I'm upset I was told about me taking advantage, then attacked for wanting a sitter, then being asked to pay for my own mother to watch her grandchild but my brother throws his 3 kids at her almost every weekend and that's A OKAY.

So I'm looking into babysitters now because there are times when me and my hubby want to do date night but I don't bother asking for this very reason. I even ask weeks in advance sometimes. I don't expect anyone to say yes because my kids are my responsibility. I just don't like that I'm being told I take advantage when my mom babysits maybe 3 times a year...maybe even less. And funny how my sister is saying I take advantage when she has her boyfriend constantly washing his clothes, eating my mom's food and borrowing money but OKAY. I'm just scared of trusting someone I don't know with my babies.