I don't have twins, but I'd advise you to look at the Cybex Aton car seats instead of the Maxi Cosi. They use the same adapters for strollers. The Maxi Cosi is not a favorite in terms of install, etc. The Cybex is amazing except for the crappy canopy. I have a Bugaboo Bee and snap it in with the Maxi Cosi adapters. It also fits small babies very well.
A friend has the Donkey and I think it's a great stroller, I would totally get one if I had twins or closely spaced kids. You could also look at the Valco Spark Twin and the Stroll Air my Duo (both have reversible seats).
On your OP you mentioned Bundle Me's for the car seats, that's a big no-no, they're ok for the stroller seat but are unsafe in the car seats since they interfere with the harness (same reason you should not put bulky coats on kids in car seats, they can compress in an accident and the harness would be too loose to protect the child). For car seats you should look at shower cap style covers, JJ Cole has
one.