Taffy
Your issue with Captians at your level is one hell of an incentive to get promoted. When you progress you will find (particularly for League Teams) that the Captin is not in post because he can do at least one of the following:-
Knows where all the grounds are so can lead the convoy.
Will wash/organise washing the kit.
Can collect £3 off everyone before they feign poverty/scarper.
Until you get promoted you will have to play the hand you're dealt in terms of the Captains. Use Adam's tools for putting the onus on them to sort their team. Some will respond but most won't. Keep at it. It gets easier - honest.
Some good tips further up too.
At the toss (do it 1/2 hour before kick off - NOT just before you kick off - again I appreciate some lower teams will piss about getting out/warming up/going in/turning up late/getting lost etc etc) speak to both Captians and tell them that you will expect them to sort out any issues with their teams whether that is discipline with a small or a big D. Then you can use the phrase "we spoke about this earlier" safe in the knowledge you have done your bit pre-match.
The worst Captian I ever had was a surly youth skipperng the 2nd XV of a L4 club who on the back of a thrashing at home was getting the tit on with me. I spoke to him about repeated infringements and asked him to have a word with his team. After refusing to look at me in a "Kevin the Teeenager" stylee whilst I spoke to him he waked off back to his team and bellowed
WORD at the top of his voice.
Needless to say after 2 quick YCs against his team he tried coming back to speak to me and I spoke to him in a "Steve Walsh the Referee" stylee (see his fine man management of Stephen Hoiles of the ACT Brumbies from a few years ago :biggrin

and effectively shut off the communication channel with him - not a proud moment but I'd driven 100 mile round trip to deal with that w@nker. I blew up a few minutes early with the agreement of the winning Captain because at least 16 of us were fed up with knob head. Spoke to blazers afterwards and they informed me he was Captain because he'd Captained of the U16s once.