I had purchased some mini-teacups and had them presented on the counter when our guests arrived along with a small tea spoon and a colorful tea bag in each. These became our "thanks for coming" take-home gift. Online, I had found theme decorations. Salt and pepper shakers, a tea pot, cups and saucers, and mini decorations. Our home was decorated with all things Alice in Wonderland. We visited, played Alice in Wonderland the movie, had different card games out, enjoyed a tea party, as well as hosted a best-costume contest. You could certainly add croquet if you are doing an outdoor, garden-party theme.
For food, we stayed in tea party mode with tea sandwiches, red M&M's for the guests "to stay in Wonderland", and our beverages with a sign that said "Drink Me to become smaller". Chips and dip were placed in Cheshire Cat bowls. Use your imagination on your decorations. Since this tea party was also called the "Unbirthday Party" this would make a great birthday party theme for someone who no longer wants to celebrate their age, like me!