If I remember correctly Imbue gives your familiar the spells in the form of spell like abilities. Since it is not actual casting, it would not provide the ability to use scrolls and wands. The benefit of the UMD approach over any other is the the +19 UMD can be used on divine as well as arcane. Being able to get healing to a downed party member without using the actions of another member (which could be used to help end the fight instead) has an unquantifiable value to it.
That being said giving your familiar a Wand of Magic Missiles(Cl 9) is just awesome, if you don't mind burning treasure. If you do not like the idea of burning treasure at a rate of 125gp per round then there are reuseable scrolls from Eberron, though at a higher check. Since the familiar has a high chr, you do not need to worry about the normal stat requirements since you can use sorc for arcane and favored soul for divine. This leaves the roll for emulating a class ability (spell casting). You achieve a caster level equal to your check - 20. Thus you need a DC 29, yet if you exceed 20 you still emulate a caster level, thereby giving you a caster level check to successfully use the scroll. To make the reusable scrolls a worthwhile investment your party would have to use each one 10 times.