Disney world 2017

I know it's a very long way off but the thought is giving me anxiety! We done America and Disney last year with my then 2 year old and 8 month old. 
We are now planning to go November 2017, then I will have a 1 year old (just) a 2 year old (almost 3) and my daughter will turn 5 while we're there. 
I don't know whether I'm getting anxiety because I'm pregnant but I'm so scared of losin someone at the parks! I've done the parks lots before but the thought of taking 3 kids 5 and under has me so worried. 
Any tips for me? Just to ease my mind? My partner and I are outnumbered 😐 even thought of getting a double stroller for my 1 and 2 year old and a single for my daughter just to use at the parks. 
I am a worrier!