What other options did they have? Buffy wasn't coming up with ideas that were any better and his idea wasn't terrible. It just wasn't foolproof. Unless something else came along they were going to have to work with what they've got.
Getting up there would be another matter entirely.
"Once I'm back to my Buffy self we're both out of here," she promised him, substituting the word slayer for her name. She'd have some explaining to do after she bulldozed their way out of there, but it was better than waiting for things to go all Cuckoo's Nest.