Will a sequin lace wedding dress look out of place in a low key daytime wedding?

We're planning a low-key daytime wedding with a very small number of people followed with a lunchtime party at home to celebrate. I had been leaning towards a slim fitting sheath style dress with sequin lace for a shimmer all over. My friend has advised me to drop the sparkle and go for a more flowing dress, as she thinks that for the sparkly dress I'd need a more formal "black tie" dress code. Although both dresses look good on me, I associate more flowing dresses with feeling "pretty" and I'm after an elegant look which I associate more with the sheath dress. Our dress code for party guests is "cocktail attire (ties optional)". It's not too late to change the dress code for guests to something more formal and we could push the party timing back to late afternoon / early evening but with the party being at home (on our deck) she thinks black tie will probably look out of place. How formal / later in the day would I need to make the party for the sparkly dress to look appropriate?