How to dynamically add daemon & to end of curl

On my first run I need curl to run and wait for response. DB has a trigger that updates a field and I need to wait for that. Then on all my other curls to run on separate threads. I cannot use the parallel options for curl as the version we have does not have it and I cannot update it anyway so I have to go old school and do

for ...
  curl "some curl options" &
end for loop

wait # this waits for all the threads to finish

So I need the "&" sign to be set after the first run. FYI my curl command is 20 lines long and I did try this at the end of the curl command but it doesn't work. Trying single and double quotes around the & sign doesn't work either and give me "unexpected end of file" error.

$(if [[ $firstRun == false ]]; then echo & fi)

You could write a wrapper function to conditionally run its arguments as a command in the background:

conditionalbg() {
    if [ "$1" = true ]; then
        shift
        # run the passed command in the foreground
        "$@" &
    else
        shift
        # run the passed command in the foreground
        "$@"
    fi
}

...
runinbg=false
for ...
    conditionalbg "$runinbg" curl "some curl options"
    runinbg=true
end for loop