Summer Jobs

Really needing a summer job from mid-June to early September, but I'm a bit nervous as to my requirements for hours, etc.

I work in a nursing home 5 - 7 pm on no set day. So one week I could be working Monday & Tuesday, the next I could be working Wednesday & Friday. It's because of this that I need to be available every day from 4-7:30/8 PM ish.

Which means I can mainly work mornings. Which is fine. However, I would like to start work (anywhere) ASAP, which means from June 16 onwards, but I have three Open Days coming up which means I have to take time off work (one of which I have to go up for the night before). Would employers be pretty irritated with me? I wouldn't mind working nights but I don't know if there's any age restrictions (I'm 16).

I'm sure no-one would employ me if I say that I can only work mornings/until 3 PM, with me already asking for a few days off in June/July.

I can't work in the home because carers do the breakfasts and lunches, and if they're on holiday, they have to have staff in qualified to do their other duties other than the food periods.

Thanks for any help!