going to a wedding in Italy in mid-May - dress me?

[Burren]

Advice sought - I am attending a smart wedding in the Abruzzo in May, and have nothing to wear. Your challenge is this:

I live in the middle of nowhere, with limited childcare and no car, so purchases will probably have to be online.

I am a post-baby size eighteen, and very self-conscious about it. Large breasts and don't ever wear sleeveless clothes.

I can't wear heels, so whatever is proposed will have to be wearable with flats.

I really dislike dressing up, and feeling in any way constrained, and I will have a toddler with me at the wedding, so no point in anything too elaborate/easily creased etc.

(To give you some idea of my usual style, at the last wedding I attended, I wore and grey and black linen long dress with an umbrella hem and a thin black cardigan over it.)

Long Grecian style gown springs to mind, not white of course!

Like this, gold jewellery, hair loosely up, flat braided sandals?

www.johnlewis.com/somerset-by-alice-temperley-jersey-grecian-dress-red/p975210?s_afcid=af_79682&awc=1203_1398259511_d7012c7d4abae263d897611c28ddc5cd

Not sure what your budget is

I like this

www.debenhams.com/webapp/wcs/stores/servlet/prod_10701_10001_62076+150721012_-1

This depends on your colouring I think

www.debenhams.com/webapp/wcs/stores/servlet/prod_10701_10001_008010240676_-1

black dressed up with gold/bright accessories?
blue or green print wrap dress
cobalt cocoon
blue
leopard
plum lace?

Faux, several of those are lovely, but I don't think any of them are wearable with flats, really..? Feel free to disagree - as I know nothing about clothes and resent any occasion I can't attend in jeans (in fact I wore jeans to my own wedding...) - but I think knee-length dresses look weird and stumpy without heels.

That Alice Temperley dress is beautiful, as is the blue long dress EatSleep suggested, but I have a horrible feeling either would make me look like a sack of spuds with a string round the middle... I just feel lumpen at the moment, and though I have plans to do something about it, I'm at the end of a book and won't get far between now and the wedding...

Thanks Faux, Eat and Apatite - any further thoughts from anyone welcome. Budget is no problem, as the one thing about being a writer living in the sticks with a small child, is that I don't make any impulse purchases...

Recommendations for beautiful flat shoes or sandals that would work well with a long dress also welcome.