6 year old boy party outdoors...in January...possible??

[snowdropparty1]

Hello, My son will be six in January and we would love to involve the garden in the party but not sure if this is really a good idea or not!! Thinking of a covered bouncy castle and serving hot food, hot chocolate inside. I am noit sure how this would work in rain or even snow which is also a possibility...perhaps we could cover the 'walkway' with gazebos? If anybody has any ideas, tip or experience with this sort of party or other suggestions to use the outdoor space I would love to hear from you! Thanks!