I'd take a small kit including plenty of microfibres, bottles of quick detailer and glass cleaner, glass cloth, packet of baby wipes, bottle of water. Unless you are planning to actually wash it during the trip, that should cover most eventualities. If it gets filthy you can always just use the local garage jetwash to hose off the worst. The rest can really wait till you have returned and gave it a proper wash. If you have a cool bag, pack it in that then just tell your other half it's a cool bag, a necessity.
Have a great trip.