What I mean is that I feel bad for him if nobody comes because it is at his house. Not that I feel bad because his parents can't afford anything else. I just picture this 6 year old all excited about his party and then being so sad that people did not show up.
None of the other parents know his parents either so hopefully other parents plan on staying too. I have emailed a couple of my DS's playmates moms to see if their kids are going.
I am sure that his parents are very nice, it is just something that I have never had to deal with before so I am a little nervous about it.
I've attended dozens of kindergarten parties, about a dozen at homes, and not once have I heard about anyone considering not letting their child go because of this reason. They either chose to stay, or chose to drop off. I can't imagine not sending my child just because it's a home party. I actually prefer them, since they're usually right in town.

And she was in 3rd grade!
My son wanted his at pump-it-up and I was so happy because I know how much harder an at home party is. And frankly, it probably would cost just as much to have an at home party.
When we get a party invitation we look and see if we can fit it into our schedule. If we cannot then we decline. We are usually able to work it out somehow.
As for activities, I'm guessing my kids are older - ds11 is on 3 teams this spring, down 1 from the 4 he's on in the fall. Dd9 dances 4 times a week, and competes about once a month. DH coaches ds11's travel soccer team, plus dd7 and ds7's soccer team. He also teaches a college course part-time. Between soccer, baseball, softball, basketball, dance, gymnastics, voice, theater, scouting, and tae-kwon-do, we really don't have time to spend 2 hours at a classmates home on the weekend.