Suggestions for 3yr old's bday party

[PDR]

which doesn't involve me having them all in my house!!!!!!

We do have a big garden but not sure what I would do if it rained!

Hey I noticed you haven't had any replies to your post. It's really simple. Pray for good weather, but plan for rain. Organise a treasure hunt outside and I'll guarantee even if it rains they will be queuing up to go outside and find their treasure. If it is a complete wash out you can do it inside instead, but make sure you also have a craft activity to keep them occupied.
Try this website they have some great suggestions for party planning

Soft play centre, safe, they love it and everything will be done for you.