what sort of things does your mum like Danni? are you wanting something from yourself and DH, or something more from Mason?

things my SIL and I discussed for my mum were:
- digital photo frame (Bro has three kids, so she'd always have new pics)
- candle set (with a poem of thanks similar to what you got for M's godparents)
- voucher for a day of pampering (massage/facial)
- pamper pack (candles/aromatherapy stuff/oil burner/aroma melts/bath bombs etc)

i know how hard it is to find unique things - i think sometime putting your expression of gratitude on the card you give means more than the actual gift itself...