[Babul]

you can (and should) use the native checkpoints for missions. imagine you are in blueberry, and got 2 deliveries: one to KACC military fuels (north east), and one to the saw mill in angel pine (south west) - both checkpoints are at the same distance (like 3500 units?), so when you drive a circle around blueberry, both checkpoints will swap being displayed. the closest checkpoint always is visible, unfortunately only 1 can be displayed at the same time. if you intend to make a mission with single targets, then the streamer is senseless - if you want multiple targets where the closest one displays, then the streamer is the best way to go.
oh, have a look here: https://sampwiki.blast.hk/wiki/SetPlayerCheckpoint
you can add 1 more checkpoint by using a race checkpoint, with a certain type (am too lazy to seek it up now lol), it wont display the arrow inside -> you got 2 checkpoints to work with, 1 normal, 1 race (but its a bad idea: no race filterscript will work properly, but who starts a race when delivering and vice versa?)