I understand about the garage sale, but I wouldn't let the kids get away with "we don't want to sell anything" if you'd rather go the ebay route. This is their trip too and selling off some toys that they dont play with anymore, gently used clothing, etc. is a great way for THEM to contribute to their own trip.
If it were me, I'd tell the kids (assuming they're old enough) to each pick five things to sell, just to get started. Give them the control, they know best what they'll miss and what they haven't touched in six months.
That asside, do you have any grown-up "toys" that you could sell to raise cash? Gadgets and gizmos that you got as gifts and don't really want/like? If you wear designer clothes and have some in good shape that you don't need, you could sell those through a consignment shop perhaps. Take a good look around the house, you'd be amazed at what you have laying around that sell, and it's sometimes funny the things that fetch the highest prices.