DNS Redsign

In my scenario i have recently purchased a public IP pool from APNIC. We have two ISP's ISP-A and ISP-B both are connected to my firewall by static IP. In my firewall they are configured as fail-over concept. I want to advertise these new IP pool on both the ISP's. So that if one ISP-A goes down the server run at my end will run by other ISP-B.The ISP peoples are tell for advertisement this new pool ip need to run BGP at my end in my firewall. As of my knowledge it is not require to run BGP, It works by static route at both the ISP's end. When a user try to access my site in internet 1st it will resolve and get my new public ip then it comes with the both ISPs gateway to my firewall end .Firewall decide to send packet data by which link ISP-A or ISP-B, because in my firewall ISPs are managed by SDWAN concept. Please rectify me if i am wrong. Thanks