I usually advise anyone using wifi extenders, that if they're needing more than 1 to switch to a mesh system like orbi or MK nighthawk.
but it can be done if you do it properly.
a couple questions.
1. what extenders are you looking at?
2. are you planning on setting them up in a star or daisy chain configuration?
3. are you planning on disabling smart connect on the router so you can connect each extender to a different 5ghz from the router?