One word of caution, if you do any Multiple Lift and someone sees you setting up the double or even worse, they spread the chances are that person will look again and again and again for two cards. There are many tricks where it is used, and you will find you wont be able to do them for your family if they suspect that you often show two cards as one. And once they get an idea in their head it will be the solution to every trick with cards you do for them. And they'll probably let you know it too! - On the odd chances it happened to me I act as suprised as everyone one else. "TWO?! I wont have to buy many more packs of cards if they keep breeding at this rate!" And I dont setup another double until their signing their card or something. But those times become rarer and rarer the more you practice. Think about the setup - no need for them to know, talk or point to someone and have a chat about mental energy or spirit guides etc then you're all setup ready for when you want to take it off the top.
Personally, I play most of the stuff I do as This is a deck of cards, I am me, here is reality, but there are some crazy places in between. After some harsh lessons I made sure that for the spectators the cards would always just be old bits of card, but the fact they move about, turn face up,vanish etc is what we magicians exploit and there is very little skill involved. I find this sets the spectator on my side, I want to see something happen as much as they do. Also, think of your routine. If you have royal road there's a bagful of tricks. Get a really simple one and learn it, learn it good

Then show your mum, while shes still reeling from the effect and trying to work it out, you get ready for a DL. Pick up the double and display, turn down, put the indifferent into the middle and pass her the deck as you square it in fully. This is where I feel you should emphasise you will DO something. The magic is done, milk it for a little bit, then tell them to turn the top card. They will remember - wow it was put into the pack and i had my hands around it so he couldnt have touched it etc etc!!!
However, bad bad idea to just get out a deck of cards at dinner, say here is some magic (they are looking for hanky panky from the start now) I cant stress how much misdirection and emphasis play a part. Then fumble with the DL as they watch your everymove, hold the two cards like they're some ancient manuscript then just thumb off a card and jam it into the middle of the deck. Its not magical, its not believable and its embarassing for everyone. Especially the performer - been there, done it, got the tee shirt. Then magic is not so much fun
Good luck, if you use it sparingly and do it well the DL is sooooo powerful. But done badly, people will twig and then youve got problems. Even if they suspect its bad as they'll be looking for you to do a funny move. I just met with a friend from college I hadn't seen in a year and a half. The barmaid in the bar we were in had a deck of cards which I borrowed and did an ambitious card routine for him. I was nervous of my DL as I'm still tweaking but he picked my up when I riffled the front of the cards. "Ah a riffle pass" He said.
"What?" was my shocked reply, "whats that?"(deny all knowledge!!!)
We had a magician at my Sister's wedding, he showed me a trick and he did that riffling thing and when I asked him he said it was a riffle pass.
Thankfully I was setup for a DL and could show it placed in and returned to the top cleanly, taking his mind off the riffle and the notion I was not playing fair

But what a situation! And for what, it wasnt even anything wrong on my part, it was someone elses attitude to magic - and worse it was a fellow magician. Practice, Practice Practice!!!!
James