age, daytime outside pen and nail/ teeth care

by Mel
(Caribbean)

Hello
Like some other bunny owners here, my 2 bunnies, Starlight and Cinderella (supposedly both females), were an impulse buy - although i did go home and do an hour's research before going back to the pet shop!
I'm not sure exactly how old they are - from what the pet shop guy said (and he's no expert tho very pleasant) they were about 5 weeks when I bought them and that was 2 months ago. The texture of their fur is currently changing from baby softness to something more closely resembling silky cat hair, and the colour is changing in patches.
They currently occupy our second bathroom that we've surrendered to them until we can build their outdoor pen, and among other things love to jump onto the toilet seat then up on the tank!!

They feed on grasses, herbs, veggies, pellets and fruit (and cardboard boxes, lol) and I groom them whenever they permit me, but they prefer to run around like crazy things and climb and sniff me and be hand-petted than be brush-groomed...

We take them out almost daily for a few hours' exercise, but the plan is to convert an existing grow-box in the back garden onto a covered pen for them, It's about 10 ft x 4 ft and we plan to enclose it completely - roof and all- with PVC and sturdy wire mesh, with a wooden hutch for shelter, and grow grass and other bunny-friendly plants for them in it.

At night we'll bring them in - either to the bathroom or the 7 ft long x 3 ft wide x 2.5 ft high pen built of wire cube shelving that we currently use outside.

SO, THE ACTUAL QUESTIONS ARE:
1. About how old could these bunnies be?
2. based on the above paragraph, are the dimensions for our planned outdoor pen suitable for 2 bunnies?
3. if they are out in the grass all day, do their teeth and claws need any extra trimming? I read, somewhere, that only indoor bunnies really need claw trimming. Is this correct?
Thanks in advance - if any pertinent info is missing I'll be happy to add it!