For those trips I take my young one with me I have a older Kelty Kid Carrier I found on Craigs List for just $25, it holds up to 45lbs, and it carries pretty comfy, the kid loves it for sure.  Mine came with the full rain and bug guard, though we never bothered with any of it.  The bug guard is a cheap net, and well the trees are pretty likely to ruin it... 

Kelty has a newer line of carriers and one day I plan on upgrading to one, but this one does really well.  Most importantly it's safe and my kids has never fell out and so far they have a reputation that no child has fell out of their carriers!