Agree about the room idea - we did this and it does make it much easier. We packed it up last and set it up first. I fact, I roped in my sister and brother in law to do it for us in the hour either side of the move andthey just shut the door, looked after our DD and packed up toys, clothes and pictures - very easy and DD had a lovely time with cardboard boxes - foudn it very exciting to our surprise. I reckon if you can stay in control, as relaxed as possible and happy, they will take their lead from you and stay calm as well.
For me, the only way to do this - 1 16 month old DD at the time and 2 cats - was to plan well in advance like a military operation and work out a two week schedule of de junking, cleaning, packing and labelling. I run my life by lists and had them stuck up everywhere.
We survived by calling in a lot of babysitting favours in the last two weeks so I could get organised and being thorough when making those lists. For example, my sl moved house and only remembered about her full freezer the night before the move...stressed out, surrounded by packing boxes trying to defrost a freezer, giving food away to her bemused neighbours just wasn?t fun. Packing up a garage or garden shed can take much longer than you think so start early - same for an attic (our garage took a whole weekend!) Pack a survival box to go in your car - everyone will have their own list but I remember ours had stuff like paractemol, biscuits, T bags, flask of hot water, mugs, calpol, spare nappy and wet wipes, baby food, toys, pen and paper, mobile phone adaptor, list of important phone numbers incl., estate agent, solicitor, removal company, buyers solicitor etc.,
Remember to collect any spare keys in a advance from neighbours if you have given any out, cancel any deliveries like milk, newspapers well in advance so you don?t end up paying extra. It is nice to make a brief note for new buyers about things like what day the bins are collected, who delivers milk in the area, which companies supply the elec, gas, etc etc. etc.and a job that can be done well in advance rather than rushing mins. before leaving the house as an afterthought.
I bet once it is all over you will find that she is more relaxed than you are and actually enjoyed the excitement of the day. Good Luck hth xx