Update: Thanks for all the responses. I talked to the sensei at his dogo, and we are going to have his party there - a karate party: up to 15 kids, with pizza provided for $150. BARGAIN!
Tman is turning 6 in about a month. Last year, we used our condo clubhouse for his party and it turned out great. There was lots of room, and I didn't have to make sure my house was super clean. I just contact the on site manager guy and he said the clubhouse is not currently available for events. LAME. The struggle is that last year, Tillman had tons of kids at his party - a lot of siblings of friends. I don't want to exclude them this year, because it was actually tons of fun to have a huge party for him. I don't want to have it at a park because I hate to rely on weather, I don't have extra money to spend on a space to rent (or the couple hundred bucks it takes to do something like Pump it Up), so these are the two options I'm considering:
A) Have it at our condo. It's small, but not crazy small, and we are on the ground floor, so if it is nice, the kids can do some games outside. This would mean that we would have to limit the amount of kids that are able to attend.
Have it at a pizza place that is kind of close. The negatives of this are that we would have to buy food for everyone (it's pretty reasonably priced, so maybe $100 for food), and the party room would make it hard to eat and still have any room for games or anything. At a 6 year old birthday party, I think that just sitting and eating isn't going to be fun - at all. They need to burn energy.
Of those two options, which would you think to be the best?
Anything I am not considering?

Re: Birthday party WWYD? updated
I would either do it at your condo or do it at a park. Like tulips said, it will most likely be nice.
How much is it to rent time at an indoor pool? You could do that sort of thing - I don't think you would have to pay per child, but rather for the time.
What about Chuck E Cheese? It's got pizza and relatively cheap fun rolled into one. There's one in Lynnwood, Bellevue and Kent. If you only invited 5-10 age appropriate kids - you could probably do a whole 2 hours package - with food and cake - for $100-150 or so. They have a party builder on their site so you can work to a budget. It's gimmicky for sure but I bet he and his friends would love it!
TTC #2 for a million years: SA normal, CD 23 bloodwork shows nothing amiss, ovulation detected. Next step: ? maybe CD3 bloodwork to check eggs? All out of pocket, so limited IF tests/treatments.
Yeah that is what I was thinking too. When I was in kindergarden everyone started doing drop off kid parties. I think you should just word your invitations to the effect that kids should be dropped off at this time and picked up at this time. That way you would invite a few more of his friends without all the adults there and maybe do a little more?
You could also look into a bowling party... we did it with Ben and it was fun. Just a couple of friends since we had parents too, but you might be able to do that pretty cheap.
And I agree with the others. I'd probably aim for a park if you think the parents and siblings still need to come.
I think a Friday would be great - that still gives families the rest of the weekend.
I would say go for it. The kids are older, so a Friday night would work.
Okay, it's available from noon to 10pm. How does like 5-7pm sound, so people can get off work, and the kids don't get to bed too late.
I have a call in to his karate place. I think they might do parties, so that's worth a shot, too.
TTC #2 for a million years: SA normal, CD 23 bloodwork shows nothing amiss, ovulation detected. Next step: ? maybe CD3 bloodwork to check eggs? All out of pocket, so limited IF tests/treatments.
I think 5 would be hard for someone to get off work, get home, and bring the kids.... but you know your friends' schedules better than I do.