Running several scripts in parallel bash scripts on remote machines

in the following bash script , we want to run in parallel several scripts on remote machines

ssh $server_a  /tmp/activate_nodes.bash &
ssh $server_b  /tmp/activate_services.bash &
ssh $server_c  /tmp/activate_components.bash &
ssh $server_d  /tmp/activate_nfs.bash &
.
.
.

not sure about to put the "&" on the end of the script or some other approach ?

Note the target is to run all 25 scripts on 25 diff machines , so all runing of the scripts will be in few second , while scripts proccess on remote machine will still run until end

Running these in parallel is fine, except for the interleaved output. To save output for later analysis, you can also "tee" the logs for later inspection:

#!/usr/bin/env bash
ssh $server_a  /tmp/activate_nodes.bash      2>&1 | tee ${server_a}_$$.log &
ssh $server_b  /tmp/activate_services.bash   2>&1 | tee ${server_b}_$$.log &
ssh $server_c  /tmp/activate_components.bash 2>&1 | tee ${server_c}_$$.log &
ssh $server_d  /tmp/activate_nfs.bash        2>&1 | tee ${server_d}_$$.log &
wait