the chicks won't be out much, if at all for the first couple of days. they'll soon get the hang of the ramp (or are they bantams?). I give mine some wheat/pellets in a cage feeder that the chicks can't reach.
I don't put anything out with the existing flock until they are about ready to lay/in lay. At 6/7 weeks I tend to separate mum from chicks (but I am usually later in the year and want mum to recover and moult) and keep the growers separate until they are ready to get layers pellets.
have fun, watching mum and chicks is fab