Your picnic is aimed at letting you enjoy each other's company, so don't get overly concerned about extensive preparations and avoid having a mess to clean up.
Take your meal with you in a picnic basket--and that means one. Don't take two or three satchels full of food and a portable grill. Make it easy on yourself with some fruit like grapes, cherries or cut-up cantaloupe as your starter. Put in some crackers and a soft cheese like brie. Remember to take a knife to spread the cheese. Add a bottle of chardonnay and some chocolate for dessert and you have all you need.
If you want something a little heartier than cheese and crackers, try some simple sandwiches.
Don't use everyday white or wheat bread--that's too simple. Instead, take a flatbread and make turkey, egg salad or chicken salad sandwiches. Do both of you a favor and avoid salami, tuna fish and any other malodorous food. Remember, you are there for romance--don't kill the mood with bad breath.
If you want to go all out for your partner, start off with some pasta salads (don't forget forks).
You may want to take turns feeding each other for more fun. Cold chicken can be somewhat messy, but it also can be wonderful on a hot day. Strawberries dipped in chocolate enforce the idea that romance is in the air. Always remember to bring a great wine. You can also take a small, battery-operated boom box to play romantic music.