Need Ideas For 6 Year Old Boy's Indoor Birthday Party?

I need some ideas for my soon to be 6 year old's birthday party. I was just going to have a family get together but he wants a birthday party. We are new to this area (1.5 months) so I am not that familiar with the kids in his class and the ones I have met are "rowdy". I am unsure what to do.

It is usually snowing here so outdoors is out of the question. I have a small house so that is out too. I can get a large birthday room for free "yay" so that is not a problem. What kind of theme should I use? What games and how many should I plan for? How many children should I invite? Should it be a boys only or the whole class?

A friend suggested a sleepover, but I feel he is too young for that. We live a rural area too so if a little one got upset, it takes a while to travel here. He loves the outdoors (deer, ATV's, etc) and he loves Army men, go figure! I am alone on this project as I have no friends here to help me out. The last party was a disaster, the parents did not watch their children and I was all alone trying to wrangle 15 little ones ages 3-4. Not fun, I couldn't enjoy my son.

Any ideas, suggestions, comments would be helpful. His birthday is Jan. 27th!

Thanks so much.