Recofiguring DNS/DHCP: a bit of advice?

I am administrating a LAN with a mix of Linux servers and Windows/OSX/Linux/other systems. A while ago I configured our DHCP- (isc-dhcpd-4.4.1) and DNS server (BIND 9.16.44-Debian) to implement DDNS, which works fine. However, the address space is now looking really quite messy, with some servers having static addresses, so I want to isolate the static addresses at the lower end of the range. This is the interesting bit of dhcpd.conf:

subnet 192.168.50.0 netmask 255.255.255.0 {
  range 192.168.50.10 192.168.50.250;
  option routers 192.168.50.1;
  option broadcast-address 192.168.50.255;
  option boot-size 8208;
  next-server 192.168.50.111;
  option tftp-server-address 192.168.50.111;
  option bootfile-name "/boot/grub/x86_64-efi/core.efi";
  filename "/debian12/boot/efi/EFI/debian/grubx64.efi";
}

host bonsai {
  hardware ethernet FC:34:97:1A:D3:67;
  fixed-address 192.168.50.149;
}

...

As suggested by the host bonsai ... config, some systems are on fixed addresses - I want to move those to static addresses. To my mind it seems as simple as changing the range parameters from range 192.168.50.10 192.168.50.250; to something like range 192.168.50.100 192.168.50.250; - and cleaning up the DNS files, leaving only the static addresses. But is it as simple as this: - Stop named and dhcp - Make the configuration changes (is there a DHCP- or DNS cache somewhere?) - Start named and dhcp - Change the fixed addresses to static addresses, one by one I'm hoping to be able to do this without disrupting people's work; my thinking is that the users on fully dynamic addresses shouldn't notice the change at all - when they renew their lease, they get an address in the new range (unless there is a cache somewhere?). Am I right, though? And I would welcome any advice or opinion.