A lot of tattoo artists/parlours will ask if you are diabetic. (I wasn't when I got mine 2 1/2 years ago but they did ask me on my information form.)
I think the concern is hypos and slower healing/possible infection if they are a person with poorly controlled diabetes. However, I've heard most will tattoo well controlled diabetics of either type provided they follow the aftercare instructions (which everyone with a new healing tattoo should.)
http://blog.joslin.org/2015/02/the-safe-way-to-get-ink-when-you-have-diabetes/
As far as a Piglet on your hip, if you want it, I'd say go for it. Tattoos are a very personal decision and should be the choice of the adult getting the tattoo. (I occasionally run across the odd person who objects to tattoos in general, a friend of mine actually had the nerve to tell me she disliked my inside wrist tattoo! I told her that it was for my late son- it has his name and my tattoo was my body and my choice.) I'm considering getting another tattoo on my shoulder of Canadian Shield country (an island with spruce trees on a lake, possibly a canoe) in the next few years.
PS Don't worry about age, I was 60 when I got mine & my artist told me he recently tattooed an 84 year old man for the first time with his late wife's signature.)