My eldest daughter got married two November's ago, so just over a year. She had five friends and her sister-in-law as bridesmaids. Her little daughter, about 18mnths old, was flower girl. I went with my daughter to chose her wedding dress, along with her friends that were to be bridesmaids, luckily she bought from the first shop, a really stunning gown.
I was at my daughter's house, to help her get ready, along with the bridesmaids. Bridesmaids, groom's mum & I, all travelled in the stretch Limo together to the church, drinking champagne, all this I bought as a wedding gift, my daughter was looking forward to travelling with us, but her now husband surprised her with a beautiful special Rolls Royce, so she travelled to the church with her granddad and after of course to the reception with her new husband.
I didn't have any special duties to do in the wedding ceremony and did feel a little left out, but than, during the ceremony I was handed the sleeping flower-girl 
My daughter's sister.i.l announced she is getting married this year, but my daughter wasn't asked to be bridesmaid and after a few months delay, her daughter was asked to be flower-girl.
I think I did feel a little left out of my eldest daughters wedding, because with my youngest daughter, I walked her down the Isle, we travelled to the church together in the Rolls Royce, and I said the 'father of the bridge' speech!
Just my daughter & I went wedding dress shopping, plus her two babies
She had her & her groom's sister as bridesmaids. I paid for the wedding reception, with some input from grooms side & my D's granddad., and I paid for the RR. Such a rosy picture, but only a matter of months after this lovely wedding, I & my other D were cut out of their lives {sad] not seen them for 5yrs+ now 
Happygran I would speak to your Son and mention how you feel, without any fuss, maybe they don't realise you and his sister feel left out.