soo.. how do you get your partner/wife to try it?

i'm about to go away to a lovely little cottage for three nights with my wife for our anniversary (5 years). every now and then when we are having sex, i'll play with her sphincter, and even once i put a few fingers up there. She seemed to like it, but i'm not sure. i'd love to try it, how would you suggest I go about suggesting it to her? I mean, i'm keen on just coming straight out and asking..

what do u guys n girls think? she's a petitie/average girl (that is, petite on top but she has hips eg. hourglass type) and i'm about 8-9"

:)