A couple of things to keep in mind...
Congratulations - you just won favorite person of the year award from them, and you don't even know it yet!! There's nothing better than the gift of photos to capture sweet memories with your babes - they're truly priceless.
We ladies like to have time to plan things out - coordinating outfits, hair & makeup, etc. So while we LOVE surprises, photo sessions aren't usually the best things to "spring" on us last second. Instead of a last minute surprise, just let your loved one know that they are recieving an early Mother's Day present. I promise, they won't mind - and you'll get to reap the reward of being the best gift giver ever for days!