Hey K.. i see you've received lots of replies to your request. I shall add my two cents, so to speak! lol...
I agree with the moms that say to keep the expense of decorations down to a minimum because the one yr old doesn't really know what's going on anyway. A few simple decorations will suffice. A nice cake with Winni on top is excellent and Wal Mart makes yummy cakes!
As for the adults, now that's my favorite part of your request for help! I gave a nudge to the adults attending my party. They are usually hesitant to participate in the games but once you get them started, it's all fun from there. They love the mild competition! I went to the dollar store for some simple inexpensive gifts for the game winners. A painted coffee mug filled with things like nail polish neutral colors, and girly items for the women. Perhaps something similar for the men. Once you look around you will come up with prize ideas quickly and inexpensively. The games were along the lines of blowing up a balloon the fastest using that old-fashioned tiny straw with that gooey stuff attached to the tip. Do you remember that stuff as a kid? You can make a three-legged race across the yard using couples as the teams. Bubble gum blowing contest for the biggest bubble that does not pop on ones face! Make it silly, fun, child-like for the grown-ups to relax a bit from being parents for just a few minutes. Trust me, everyone will have a blast and will remember your baby's 1st birthday for yrs to come!
Good Luck with the party. Have fun with it. Yeah and grilling outside helps to lighten your load since the men do the grilling!
God Bless you and your family,
d.maria