I am playing a conquest paladin and will be picking up magic initiate to get a familiar. The character's crest is a hummingbird and I wanted that as a familiar. I am planning on summoning a mount at 5th and want to get a giant wolverine. I used a combination giant badger and worg to generate the stats I was looking for. check them out and see where I overplayed my challenge rating allowance for these please. Thank you.

Familiar: Harbinger
Hummingbird (Celestial)
Tiny Beast (CR 1/8)
AC: 13
HP 1 (1d4-1)
Speed: 5 ft. fly 50 ft. (Hover)
STR 1 (-6), DEX 15 (+3), CON 7 (-2), INT 6 (-2), WIS 12 (+1), CHA 6 (-2)
Skills: Perception +3, Stealth +3
Passive Perception 13
Alert: +5 bonus to initiative, can’t be surprised while conscious, and other creatures don’t gain advantage on attack rolls against them as a result of being hidden.
Flyby: The hummingbird doesn't provoke Opportunity Attacks when it flies out of an enemy's reach.

Mount: Mr. Fluffy
Giant Wolverine (Celestial)
Large Beast (CR 1/2)
AC: 13 (Natural)
HP: 26 (3d10+8)
Speed: 50, burrow 10
STR 16 (+3), DEX 13 (+1), CON 14 (+2), INT 7 (-2), WIS 10 (0), CHA 6 (-2)
Skills: Perception +2
Senses: Keen Hearing and Smell
Passive Perception: 12
Keen Hearing and Smell: Advantage on Wisdom (Perception) checks that rely on hearing or smell.
Multiattack:
Bite: +4 to hit, reach 5 ft., (1d8 + 3) piercing
Claw: +4 to hit, reach 5 ft., (2d6 + 3) slashing, Target must succeed on a DC 13 Strength saving throw or be knocked prone.

Hummingbird would be Cr 0. Giant wolverine looks about right. 

Thanks. I wasn't sure about the Hummingbird's CR. I used a hybrid of the tiny bird and owl.

I also kept waffling over whether it is overpowered to have a mount with multi-attack and a trip (13) combo. I just realized I was basing it on a hybrid worg/giant badger design. Worgs are in the wolf line of monsters, so I should just drop the trip feature. Bear, badgers, etc all have multiattack.