I got my first sari in Southall, which my Indian friend said was like someone chopped a tiny corner of India off and dropped it in London.
The lady in the shop showed me how to tie it.
IMHO it is ideal for breast feeding, you just have material over your chest.
When you buy one ask for the blouse, underskirt and there is also a bit of material you sew inside the front to make it drape correctly.
All saris are 5m of fabric and fit everyone, you just need the blouse in your size, I actually made my own for a wedding.
Also check where the wedding is (it might be multiple days) in some places you have to have your legs and head covered.
Also although the traditional sari is just material you can get ones that have been sown so they are more like a dress.
Watch out for 'the aunties', these are a mafia like group of older ladies who may or may not be related to anyone else but everyone calls them 'auntie', their mission in life is to feed people, It doesn't matter you have just had a big meal, they will try to feed you snacks.