They are not commanded to pick up snakes, so there is no justification for snake handling in these verses.
Seated at the right hand - Mark 16:19
The description of Jesus seated at the right hand exalts him to the place of ultimate authority in the universe. See 14:62 and other similar New Testament affirmations such as Acts 2:33; Eph. 1:20-23; Phil. 2:9-11. See WCF 8.4; WLC 51; WSC 28; BC 35.
Early Church history - Mark 16:20
This verse goes further into the history of the early Church than any of the other gospels. The preaching ministries of the disciples are elsewhere reported in the Book of Acts. In those reports they are carrying out the ministries to which Jesus had called them in Mark 1:17.