I did this when we moved my daughter from Washington state to NYC for college. We used our two free checked bags as boxes...for a total of four boxes. We each carried a small carry-on for our clothes/toiletries and her computer.
We used U-Haul Large boxes that measured 18" x 18" x 24". You are allowed 62 linear inches...we were at 60". You MUST keep each box below 50 pounds or you will be charged $75.00. Use your bathroom scale and aim for 47 pounds to be on the safe side.
Be sure to package the inner contents well with bubble wrap and air bladder bags. You want to fill all of the spaces so the box doesn't cave in during handling. We were creative as we balanced the loads and maintained structural integrity between the boxes. It took several re-arrangements. Since you don't know how the boxes will be loaded, be sure nothing inside can be damaged if the box is upside down or sideways.
This is important: Use good quality packing tape. A lot of it! Tape all edges and double-tape all corners. Then, run the tape **twice** 1/3 from the top and 1/3 from the bottom all away around the box to hold in any settling that might cause bulging. This prevents the box from splitting.
Label inside and out and be sure the baggage label is correct for your destination. In big numbers, I labeled the boxes 1 of 4, 2 of 4, 3 of 4, 4 of 4 thinking it might help the baggage handlers in loading if they knew four boxes of the same size were being loaded. Who knows?
We packed everything from linens, pillows, towels, clothing, shoes, shower caddy, over-the-door hooks, a small nightstand, a desk lamp and nightstand lamp, decor, snacks, toiletries, school supplies, cleaning supplies...everything she needed. We had very little to purchase (NYC is expensive and college items get picked over quickly!) once we arrived.
Also, consider how you will transfer your boxes to the college. The boxes I used were too big and bulky for a regular cab or car rental. Even one box would have been a tight fit in a cab trunk. I used a shuttle service and requested a van for pick-up. Everything worked perfectly!!
Good luck and happy traveling. These are exciting days for you and your kiddo!!
