do a little tiny latex mould of her hand, and then make a cast of it and make a keyring, so he can hold her hand wherever he goes, or you cold do it with a foot, but i dnt think thats quite as cute, plus hard to keep babys feet still for very long ! !!!
How cute would that be. . . VERY, plus you could do it every few years and be like aww look how much shes grown !!!! and when shes all grown up she can look at them !!
I think whatever you do though it'll be lovely for him on his very first fathers day !