CBW Answer: Why not take a different tack and try to channel their energies into an area of the wedding that you would appreciate their help on.
Maybe they could save you time, rather than money and help collect and return suits or arrive early and help set up the reception venue, for example. Maybe you could allocate them important roles so that they still feel they are making a valuable contribution. Ask them to do a reading or poem during the ceremony, be a witness, make a speech...
That said, I really can’t help feeling that you are blessed with having such a lovely family who are willing to go the extra mile in making your day so special. In my experience as a wedding planner, some of the wedding cakes and hand-made favours created by ‘gifted amateurs’ in the shape of mums, aunts, sister, dads and other family members are some of the best I’ve seen, and they give your wedding a really personal touch!
Photo credit: http://www.helenjonesphotography.co.uk/
Favour bags hand sewn by groom's mum, with pretty fabric sourced from the USA.