Is this outfit too casual for a summer Christening?

[leakyR]

Dniece being christened in late June, dh is to be godfather and the whole thing will be taking place in London. SIL is tall, willowy,always really well groomed and put together, her friends are also v.soignee and make me feel like a short, fat, northern frump.

The budget is tight so I don't want to buy anything that won't get plenty of use afterwards.
I bought this dress at TK Maxx, as it's summery and colourful for me but not so dressy that I'll not get more wear out of it. I was thinking nice mani- pedi and taking time over hair and make up will help my confidence. I now need shoes.
I love these, I don't do heels and think I'd get a lot of summer and holiday wear out of them. Will I look ridiculously underdressed?

I think you'll look fine if you feel comfortable, you'll look much nicer than if you force yourself into something that's just not 'you'

In honesty, it's lovely but I think too casual. It's really thin, more like a kaftan / tunic to be worn over bikini or leggings. It could be a dress in high summer with flat sandals, but I don't think it's smart enough for a formal occasion, sorry.

It is lined Yoni, so not as beachy looking in RL. I will use it anyway even if I don't wear it at Christening. Would more of a wedge/flatform sandal gam it up a bit perhaps?

Also I am short 5'3, so it hits me just above the knee.

I love those shoes! Agree that the dress does look a little flimsy in that pic but if you have seen it with the lining in rl then I think it would be lovely for a christening. Might look more 'dressy' with a small heel or I like the sound of a wedge too.

Re shoes I've been doing a bit of research and I could get away with these although realistically I'd be more able to walk/wrangle dc in these . I've the flat version of these which I love and are super comfy, so maybe I could manage the heels.