Just wondering why you're wanting to wean them onto bottles at this age, particularly if you've been having a hard time lately? It sounds like a lot of frustration and hard work?
At this age, I'd have thought it would be easier to just keep them on mums for a few weeks more and then wean them onto hard feed/grass/hay as the adults.
If you're looking to milk the adults, I'd suggest separating the kids overnight, to give milk for you in the morning, feeding the kids hay and feed overnight, and allowing them to access the mums during the day for milk.
If the mums are struggling with them and you're wanting to wean for the mothers' benefit, then that regime should help too, giving the kids and mums more concentrates to help put weight on.