Summer wedding evening do - outfit help please!

[Cydonia]

Hi, I’ve been invited to a colleague’s wedding evening reception/do and I’m really not sure what to wear.
I am probably overthinking it, but do you dress for a summer wedding, ie fairly formal, flowery dress type thing? Or more of a party outfit? I don’t want to look too ‘daytime’ as if I’ve got the hump that I wasn’t invited to the whole thing 😂
But I don’t know what to wear to be more ‘evening’ If that makes sense!
What doesn’t help is that I’m also feeling very old and fat right now so struggling to find something I would feel happy in. I’m a short, busty, large tummied size 14-16 so there’s a lot that doesn’t suit me!
Any pointers greatly appreciated ☺️

How about this? Perfect for evening but could be worn for daytime on other occasions. I’ve linked the more expensive lace version but it costs less in cotton. Almost limitless colours and a nice range of sizes. Scroll through photos to see it on different shaped models.

https://www.hillhousehome.co.uk/collections/uk-all-dresses/products/the-collectors-edition-ellie-nap-dress-navy-lace

That is really pretty, but way over budget and I would need more of a sleeve. I love the lace though, that could definitely work as more of an evening outfit. Thanks!