Creating a Frozen family costume nightmare!

Suggestions please! I am in the process of turning an old prom dress into an Elsa costume for myself, Sven for DD9, Anna for DD12 and Olaf for not so happy DH. My sewing machine is currently being borrowed by a girl scout troop and not likely to be returned anytime soon and I leave for Disney next Wednesday! Did I mention I haven't packed yet?!

The most important question I have is how do I comfortably turn a strapless dress into a non-strapless dress without making it an itchy dress? I don't want any wardrobe malfunctions when I get off a ride.

Thank you!!!!!!!!!!

Since you don't have a sewing machine at the moment, and with the idea of making it easier on yourself, what about getting some sort of white body suit to wear underneath - not exactly like this one, but you get the idea.

I have nothing helpful to add, but I really want to see pics! Especially DH as Olaf.

Love the bodysuit @Ellen1976! But I will die from the long sleeves. I finished Elsa and Anna costumes. Ugh can I scream holy freaking glitter right now! I left all my pieces separate so I can pin on for party and remove if the fabric gets too itchy or I get a hot party night. I attached the dress to a strapless bra and wrapped the fabric around it. Now onto Olaf and Sven. Need to find some shaggy animal hair for DD9's shirt.

Sounds great - can't wait to see the pics!