You threw me w/ the term "unisex" because I thought you meant "gender neutral" because the sex of the baby was not known...but now I believe you mean "co-ed" because the guests will be both male and female.
My sister and I have both had co-ed showers so here is what we've done:
Food - meatballs, sandwiches (or sandwich fixings), chips and dip, crackers and cheese, and veggie tray.
Decor - always varies based on theme and you don't mention what if any theme is on the invitations but one we really liked was the "clothes line theme" which will vary a bit based on how you do it (if shower is for a baby boy or girl or keeping it neutral). Ask guests to bring an item to hand on the clothes line (onesies, t-shirts, pants, sleepers, outfits...anything, in various sizes (you can specify colors if you want). Then you prepare a "clothesline" when you set up for the shower, complete w/ clothepins, and you or the guests hang these items....they serve as both decorations and gifts. When we had small tubs/laundry baskets w/ baby items as the center pieces (each with different items that then become gifts for guest of honor). One tub had laundry supplies, one had diapering supplies, one first aid/medicines, one with items for mommy and/or daddy to be, one w/ keepsakes. What we did, was each of us took responsibility for one or two tubs since it ended up being part of our gift to the expectant couple.
Games: Baby Shower Bingo, Guess the food, How do you know the parents to be, Don't Say Baby, How Big Is Mommy To Be's Belly, Baby Shower Word Scramble....if you aren't familiar with any of these PM and I will explain.
Another thing we've done when the expectant dad was definately attending the shower is that we had a few items specifically for him to open...box of baby cigars to hand out (we have done the gum and/or chocolate ones but you can also do real cigars if you want), "Dad's Diapering Belt" which was a tool belt with baby powder, diaper ointment, diaper, duct tape, safety glasses, rattle or other small toy, ear and nose plugs and some other gift (like a Daddy & Me frame or book of some kind).