Think of what you would do with a son who wasn't into the stereotypical 'guy' hobbies of camping, fishing, cars or sports?
There are plenty of non-gendered activities that you could do that would still satisfy their feminine side. How about going to galleries or museums? Or getting all dressed up to go to the opera or play in the city? Or ballet - what girly girl doesn't love ballet?
What about cooking or even taking a cooking class together? Ask them to help you make a special dinner for their mom, plan the menu together and go shopping for fancy ingredients. Pottery painting? Ice skating? Movies? Going out to eat? Hell, even go shopping with them - ask them to help you pick out some new clothes. I'm betting they would love to give dad a clothing makeover!
Be open-minded and have fun trying them on! Let THEM take the lead and choose the activity, don't force it on them - but make it clear you want to do something all together, and be willing to participate.