I just went to my friend's son's 1st birthday party and it taught me a lot about what I should (or shouldn't) do for my son's birthday. Something I think is important is your child's disposition. Is he social or shy? The kid whose party I just went to is very shy, so he cried through most of the party because there were a lot of people invading his space. I don't think I'll have that problem with my son (his 1st birthday is in a couple of weeks). He's very social, and always is making friends at the grocery store, etc. Also, if there are going to be lots of kids there, you might want to have some gift bags or something that they can play with because all the kids at the party I went to were "stealing" the birthday boy's presents/toys because they didn't have a lot to play with on their own. That contributed to the kid being upset, I'm sure. I do think that having the 1st birthday at home is a good idea in case your son gets tired, upset, or just wants to have a good time. Being in his own environment will help to make it more fun for him, no matter who else shows up.
I hope this helps! We're planning a gathering with about 10-15 friends and family, but we're doing it at home for a limited time. Oh that's also important -- make the party for a limited time, say 1-3 p.m. or something. Otherwise, your child can get really overstimulated and have a hard time staying on schedule (eating and sleeping-wise). Good luck!