I moved last year, a few days before DS2's 4th birthday and DH's 40th (we had a party at the new house a week after we moved, must have been mad!)
Agree with all KnickKnack's advice. I had a list of all boxes, numbered, list of contents and what room they needed to be put in. Gave one copy to the removal men and I had the other. I put the number and room info on the boxes too.
My ILs came to help on the day - they were a brilliant help. Me and MIL sorted the kitchen and DH and FIL assembled beds, furniture etc.
Agree completely about childcare for the day itself (if it's an option for you). Much less stressful if you don't have to supervise small children.
Do a list of all the people you need to contact about change of address, with account numbers, phone numbers etc. Easier to have it all in one place.
Pack up as much stuff as you can now. Get rid of anything you've kept since the last move, thinking you'll need it but have never used (old college books in my case).
Get decent removal men - even though we only moved half a mile we still paid for a company to do a lot of the work (I did the packing though).
Borrow as many boxes as you can.
Good luck and congrats - very exciting!