Worried he will ruin vaca trip

So my bf and his fam invited me to Hawaii this summer. He has a bad habit of checking out other girls and I’ve talked to him about it several times. He hasn’t done it since. But I get really down and sad whenever he does and I can’t hide my feelings well.

I don’t want him checking out other girls to ruin the trip for me or him and his family due to me being quiet and sad looking (I don’t make big scenes, I just get quiet and try to hide that I’m upset but it kinda is hard)

Do any of your so’s do the same? I mean Ik it’s gonna be half naked girls who are way prettier than I am so Ik it’s bound to happen. My plan is to have another reminder talk for him before the trip.

It’s just something that I see as disrespectful and I get insecure. I don’t check out other guys ya know. And I’m the future if we stay together , I don’t want vacation trips to be like that, him always checking out other women. I did tell him my future husbands not gonna do that.

*if there was a goddess on the beach I wouldn’t technically blame him. Like if she was jaw dropping. Like you’ll never see a girl as beautiful in your life again. Very rare type. But he does it with like every girl that’s average to hot. And he tries to hide he’s checking her out he just does a shit job*