Avoiding ticks - outdoor reception

Try looking up essential oils that repel ticks.

Buy 20% picaridin spray. It’s as effective as DEET, without toxicity & without odor. You can spray it on skin & clothes (just not on face).
When it comes to essential oils, only few are effective against ticks, but dose & application is not well controlled / known, so I would not rely on them too much.
Here is picaridin spray I have: https://www.amazon.com/dp/B07BSN5YLN/ref=cm_sw_r_cp_api_i_31SiDb4APSTQ0

Welcome to the WeddingWire community, Rose!

A picaridin spray sounds like a good alternative in this circumstance.

You could also have a member of the wedding party or a family member check you once you come back in from your photos if this will ease your mind

Will you have some repellent available for guests to use? Or will they not be outdoors much?

There's also bug repellent wipes! I'd suggest wiping everyone's feet and ankles down with those beforehand too!
There's essential oil based sprays that you can likely do on/around the dress. I'd actually spray under the dress rather than the top because ticks like warm dark places and you don't want crawling into the bodice from the bottom. If you get tick wipes or skin safe spray I'd suggest dabbing a bit under the breasts, it sounds silly but I've been camping sense I was small and under the breasts is a spot ticks love. You do not want one there!

Here's a website I found that lists essential oils to use for tick repellent:

https://commonsensehome.com/natural-tick-repellents/

Good luck!