Your holiday suitcase might be a bit too big! Some sort of weekend bag or sports bag would work fine - I've fitted all my stuff into a sports bag and that is what I used last time too. If you don't get the luxury of a side room on the postnatal ward, you'll find there isn't a whole lot of space around the bed, so something that can be shoved under a chair is probably a good idea. x
I've packed a mini wheely suitcase as my main bag; the changing bag with extras which will stay in the car & only come in if I stay an extra night (more babygros, more nappies, a spare nighty etc) and a rucksack for DH.
I'm doing the same for DD2 as I did for DD1, and as others have mentioned above. I have one bag for stuff needed during labour and a second bag (which can stay in the car) for what I will need if I have to stay overnight. Both are mini wheeled cases (ie the sort which are accepted as hand luggage on planes).
I also have a mini suitcase on wheels. (The type you can use as carry on to an airplane) I will only pack the essentials, enough to last me & baby 2 days stay at the most. I then have a smaller bag, with top up clothes etc... that will remain in the house, Hubby can then bring this if we need to stay in longer (although I'm really hoping this wont be the case!) Think the idea of a top up bag is perfect as you/hubby don't have to think about where things are! ,