For mum - Voucher for handmassage/nails perhaps
Nice handcream or candles

For the little one - bath toys, bath crayons, ball, cars. FWIW he will probably have and get heaps, I would focus on the mummy anniversary! (But that may be more about me, lol)

Not sure how you would feel about it - but perhaps instead of a gift for her, maybe take her out for lunch/coffee instead to celebrate. Maybe a cupcake at work for her if she is at work on her son's birthday?

This is such a thoughtful idea too - with my DD's birthday next week I know I would be really touched that someone wanted to celebrate her birthday but more importantly me too!!!