Can't help with the fajitas that's wifeys responsibility, but since you're doing Mexican (and assuming adult beverages will be served) get the Margaritas right. Our three go-to recipes:
Classic (a lot of lime juice, kind of a pain)
8 oz. Tequila
4 oz. Triple Sec
2 oz. Sweet & Sour Mix
4 oz. Fresh Lime Juice
8 oz. Club Soda
Pineapple Margarita
8 oz. Tequila
4 oz. Pineapple Juice
1 oz. Triple Sec
1/2 oz. Fresh Lime Juice
1 oz. Club Soda
Pomegranate Margarita (we made these tonight, yum):
8 oz. Tequila
4 oz. Triple Sec
3 oz. Pomegranate Juice
3 oz. Fresh Lime Juice
8 oz. Club Soda