How do we ask for no boxed wedding gifts when we're moving two weeks later?

Mum showed me a photograph of the serving bowl she'd chosen for us. I said it was beautiful, then asked whether she could keep it for a while. "I thought you were starting a home," she said.

We are, but we're moving overseas two weeks after the wedding and taking two suitcases each. We aren't sending a shipment of household goods. We haven't made a registry because we don't want people choosing things we'll immediately ask relatives to store.

My partner wants the invitation information to say "No boxed gifts, please." Mum thinks that sounds like a request for envelopes of cash. We don't want guests to feel they need to give either. We also don't want to open a large present and start discussing where its owner should put it for us.

How do we explain the practical problem without making people feel their idea of a wedding gift is unwelcome?