There is one option available. Create a new VLAN and create new DHCP scope for this VLAN
Assuming you created new VLAN as VLAN 20
Switch (config)#ip dhcp pool Vlan20
Switch(config)#network 192.168.X.X 0.0.255.255
Switch (config)# default-router ip 192.168.1.1
Switch (config)#dns-server 126.96.36.199
Also create the same VLAN 20 on downstream access switches, and ...
Now they have 230 devices and They are going to increase device count by 100.
Within the same subnet? Then you'd have to supernet that subnet to e.g. 192.168.24.0/23.
I cannot change subnet and increased usable IP addresses count because there are many dependencies.
Adding another subnet/VLAN is a better option anyway. As Jesse's already answered, that ...
Questions about protocols above layer 4 are off limits here, however, as a very basic explanation on a layer 2 and layer 3 level, you cannot have multiple VLANs using the same DHCP pool (same subnet). Each VLAN would need a separate DHCP pool (separate subnet) to assign addresses from.
VLAN 100: 192.168.1.0/24
VLAN 200: 192.168.2.0/24
Just to ...