you dont't say where you are located in ohio which would really impact what you can grow.
one of the biggest problems with annuals will be that their life cycle programs them to sprout, grow, bloom and set seed during a single growing season before they are killed by drought, heat or cold. with a mid october wedding you are pushing the envelope to keep them from going to seed and will need to continously dead head to force them into staying in bloom. and yes frost will dash your hopes,

so where are you in ohio, and consider all the late blooming flowers for your wedding.

diggerb

I don't think any of those from your wish list will still be blooming mid-october. Most plants 'do their thing' according to the amount of daylight each day and the temperatures so it's not something you can 'work around.' I would recommend going to get some flats of pansies around Oct. 1st and using those to decorate. They thrive when it cools off and won't be bothered if you have a frost.

Last year I decided to put in a new bed in the front. I bought a few perennials but wanted to start the annuals from seed indoors. For one reason and another the bed wasnt ready to plant until the 6th of July! The 2-3" seedings sat in their little peat pots, in the shade for two months, spindly things,barely hanging on. But they mostly survived and eventually thrived until frost (mid October here last year) I had arm loads of asters, and zinnias, both make great cut flowers. If you want something showier, Dahlias bloom until frost, plus are fairly easy to grow in containers, so you could bring them inside if the cold comes early.

So plant annual seeds late and you should be ok with many of them. (Perennials from seed dont usually bloom the first year)

These are just guidelines by taking averages over the years
Zone 5:
Last Frost Date: April 15
First Frost Date: October 15
Frost-free days: 180

And with some of the "unusual" weather across the country so far this year... ie the 3.5 inches of snow we got May 7th., I wouldn't leave everything to chance at having a garden of glorious blooms on Oct. 16th.

If the soil is sufficiently warm for seeds to germinate, usually about 50 degrees, go ahead and sow your seeds. Just be prepared with a backup plan to cover yourself for all the gardening unknowns.

I would second the vote for dahlias - they come in wonderful shapes, forms, and colors and they make stunning arrangements. In containers, you could cover them if you have frost and they'll be wonderful - the colors of dahlias are always the best and richest at that time of year.

Most of my other annuals are finished by this time - I have asters and mums in the fall (but they aren't annuals) - asters are generally finished in September here in Illinois but some of the mums are still lovely in October til hard frost. You can pick those up at garden centers at this time of year and they could be really nice filler flowers.

Don't ignore pretty foliage - you may already have some in your garden in trees or shrubs - in October you might be able to add things like japanese maples. I have a green one that turns beautiful gold in the fall along with the deep crimson red.

Do you have theme colors picked for your wedding?