The first time DH met my nieces, #2 was about four or five months old, and he was terrified that if he held her, she would break. Now, they're a bit bigger, and they absolutely adore him.
I loved watching him with #2 over this weekend - she is a very affectionate little girl, and she snuggled up to him to watch a DVD on Sunday morning and to look at a book with him in church. She held his hand and walked along with him to church as I pushed #3 in the buggy and listened to #1's endless stream of chatter. They lagged behind us a bit as she told him her stories about princesses and fairies, and he listened and made all the right noises.
Normally, although he'll play with the children, he leaves all the childcare duties to me and just takes responsibility for clearing up after meals and tidying up the toys while I'm putting them to bed. This time was a bit different, because BIL arrived after the rest of his family and so DH was left alone to look after #3 while my sister and I went off to the theatre with #1 and #2. He also handled #3 on his own during Mass, because #2 wanted to go to the children's liturgy and 3-year-olds were only allowed to attend if accompanied by an adult.
'No' is a word that's not really in his vocabulary, and he'll go along with whatever wild ideas the children think up. One time I left him in the sitting-room with the girls while I was cooking lunch. #1 had a sticker book, and when I checked on them after about half an hour, the book was empty of stickers and DH was covered - he had them all over his face, his glasses, his shirt, his hands... I asked why he hadn't suggested that she put the stickers in the relevant places in the book instead, and he just shrugged his shoulders and said, "Well, she was having fun."
Looks like I'm going to have to play bad cop to his good cop a few more times in my life - but he's so sweet that I think I'll cope...