Thank You Note Dilema

I'm a huge believer in thanking the people who have been kind and generous enough to contribute to my family.  We have been incredibly blessed with a baby shower thrown by my church family as well as another one from my school/work family.  I just finished up hand written thank you notes to those who attended my church baby shower & family.  I'm trying to decide whether to do individualized e-card thank you notes to my coworkers or if I should do all paper, even if it takes longer.  I work at a huge elementary school with about 150 staff members and many people chipped in towards gifts.  For example, about 10 people chipped in $3-5 each to get us a high chair.  Another group pitched in $2 each to get us a gift card.  I'm trying to decide if I should write individual hand written thank you notes to each of the contributors, write one thank you to the group who purchased it, or write individual thank you ecards.  I am so grateful, but also so exhausted teaching, writing maternity sub plans, writing report cards, preparing for baby, and trying to stay on top of things at home.  Any advice is so appreciated!