I had just over 80 people at my shower, and it made me feel completely loved and blessed. Opening that many gifts in front of everyone was tough. Just try to have helpers to hand you the gifts and take them as you finish. Also try to open them as quickly as possible while still showing you are grateful. It took over an hour...closer to an hour and a half...but no body really cared. My mom also did a diaper raffle and prizes, so every couple of gifts, someone would get a prize.
Just remember how wonderful it is that so many people care about you and LO already. And PPs are right, you won't have to buy much with that many people coming. Good luck, and enjoy.