We are about to move to Seachange town and my kids are seriously lazy at times. DD is a great bike rider but I am thinking there still might be times I would like them in a trailer - are they big enough for a 4yr old and 5 yr old?? Both weigh around 19kgs, the ones I have seen say 45 kgs total so Im not sure? Any other options (other than a cargo bike - not quite in my budget!)