T.O.
I remember my kids parties at that age. They're really for the adults it seems.
February makes it difficult, because you don't know what the weather will be like.
We did BBQ's and Picnics at parks for our girls (June birthdays) and for my son (February) we did the same thing, but we lived in California.
In retrospect... I'd have skipped the parties till they were 5 if I'd known how big the parties got from age 5 to 12.
But we were lucky to have the cheaper option of being outside anyway.
You could always do an outside event anyway, find a great park and just give a bad weather date if the weather makes it impossible.
Outdoors is good for that age... they can run and play on the swings and slides.