for your internal network it's no problem.
You'll use the 5400's as your local network router. Your local network sees a single router. That they use xrrp to create redundance between them for routing is no problem.
Youll use the 1841's as internet router
her also from the 5400 you see a single router, that these use HSRP to create a redundant router address is no problem.
But your problem will be at the ISP-side.
Each ISP will have it's own public address-range from wich you get a subnet.
It will be difficult to make public-adress-1 from ISP-1 reachable through the connection of ISP-2.
That you'll have to negotiate with both ISP's.
I assume your budget will not be enough to acquire an ISP-independant public range and have routing be setup using BGP at the public-internet.
Pieter