jaapbaas is telling u not to use airmon at all.
or ,if u have been using ur pc for a while and used airmon before , type the following
airmon-ng stop xx
and then start using wireshark.
At down left corner on wireshark there is 2 tabs, "Frame" and "decrypted TIKP data" So I can decrypt it using wireshark
Yes, you can use kismet and wireshark at the same time. Just be sure that wireshark is using the correct interface and that that interface is locked to the channel you want.