Hello,
fireflies,
Thank you very much for your attention to Chornobyl-TOUR

Here are the answers to your questions:
1) Unfortunately, facilities (toilets) are available at irregular intervals during both one-day and multiple-day tours to the Exclusion Zone. The reason is that the Zone is a closed area run by the government. Initially it was not designated for tourism, so there are no facilities en route.
On a 1-day trip we make sanitary stops at approximately 8:30 (pit stop at a petrol station), 10:00 (checkpoint when entering the Zone), and then 17:00 (dinner in Chornobyl town café).
So, for the whole day we might use natural toilets (bushes) in safe non-radioactive areas if necessary. Here a dosimeter becomes handy.
2) There are no restrictions to your luggage size. It will be kept in the boot of your van during the tour. If staying overnight in Chornobyl on a multiple-day trip, you may take it in your room.
3) The meeting place for a group tour: Lukashevicha str, build. 6 (old names of the street are Petrozavodskaya, Kirpy), 300 meters right from the exit of the Yuzhniy (Pivdenniy, South) terminal of the Central Railway station, Kyiv, Ukraine. See the map.
GPS coordinates: 50.4410852,30.4831796
Hopefully this information is of use to you

Should there be any questions\suggestions\ concerns about your Chornobyl tour, pls do not hesitate to contact us.
Looking forward to hearing from you soon.
Have a great day!