Rain in the forecast? The party is still on.
An indoor backup you can prepare before the weather makes the decision.

Keep the feeling, change the format
Ask what matters most about the day: friends together, a favorite meal, or a game everyone loves. Preserve that part and let the outdoor setup go. A picnic can become a living-room buffet.
Pack an indoor activity box
Choose one seated activity and one that allows gentle movement. Print conversation cards, gather crayons, and make a paper scavenger hunt. Check the space for trip hazards before guests arrive.
Tell people what to expect
Send a clear update with the location and anything guests should bring. Make the decision early enough that people can change their plans. Give yourself permission to shorten the gathering if the space is smaller.
Put a good idea into your next plan.
Keep the dates, the gifts, and the little details together.
Open my celebrations