Am I being unreasonable

Don’t feel bad asking for help?! That’s also his child!! I get where you’re coming from I have to prep everything for my partner before I go out (shopping or appointments) to make sure everything’s right for my little girl. It’s frustrating it really is. Sit down and talk? Men don’t see how mentally draining it is :( x

You’re definitely not being unreasonable! ❤️ It sounds like it’s not really about the stag do, it’s more that you’re exhausted and feel like you’re doing everything on your own. An 8 month old, school runs, shopping, cleaning, dinners etc is a lot, especially after just moving.
I’d have a proper chat with him and be honest about how burnt out you’re feeling. Maybe ask him to take on more before and after the stag do, and make sure you get some proper time to yourself too. You’re asking for support, not too much. ❤️

Ask for help, you’re 100% right !
It doesn’t matter what age your baby is, what difficulties you have, how many kids you have, what is important is that if you feel you need help then you need help. We all have diff level of overwhelming point…
Your children need you in a good mental !
.
If yiu can get help physically maybe ask your partner to prepare food for the days you’ll be alone for example. To clean the house before I leave

Ask him not to go this time as you need more support at home, you and the kids are more important than this stag

I'm going to go against the grain. It's a once a year time away and as it would definitely have been paid for he should go. It will build resentment and accusations of control if a total don't go foot down the week before.

However it's not on if throughout the year you do more than what's reasonable. Not sure if you are a SAHM but either way he must step up if you feel he isn't.

Before going away after explaining how you feel, hopefully he will do you the 4 days dinner and lunch meal preparation to just heat up and also give you some evenings just relaxing by doing more of the housework and bedtime routine, including doing this on his return.

Could you also consider booking even just a day spa after he's back so you can have time off and to yourself.