Get everything you need ready this evening, lo's clothes, nappies if needed, pack your bag with snacks, drinks, etc.
Get your stuff ready and wear your favourite outfit so you feel good about yourself.
I'd try to get it all done when they're not under your feet so you're not panicking (I've got a day out with my 3 tomorrow and I'm busy doing the same!)
in the morning, keep telling yourself what a great opportunity this is for you, you'll be meeting other people with kids who understand what its like for you.
Tell yourself you won't be stuck in the house so the kids cant make a mess there - less housework, always a bonus!
How old are your lo's? If appropriate, about an hour before you're due to go, tell the kids you'll all be going out soon. Explain what you want them to do, help you tidy up, get their coats. Say you need them to be good while you get the car seats in the taxi. Have their coats on ready and make a game of looking out of the window for the taxi. Who can see it first? What colour do they think it will be? Will it be a man or a woman driving etc? Involve them in getting ready so they're looking forward to it too.
I hate it if I have to get in a taxi with my lot, so just put a big smile on your face (even if you don't feel like it) and ask the driver for help if you need it.
Keep your big smile on your face when you arrive. Ask people simple questions, "where do you live? How many kids/how old etc?" Most people launch into conversation then and do the talking.
I've waffled on quite a lot and don't know how much will help but hope you have a great time tomorrow. Post again and let us know how it goes?
Good luck!! 