phrase requests - Is there a more accurate way to describe "short vowels" and "long vowels"?

I was taught in primary school about "short vowels" vs "long vowels". Although it is a simplistic way to teach children, it is also inaccurate, because the sounds are different, not just longer and shorter. According to Wikipedia these names are a hangover from before the Great Vowel Shift.

Long vowels pre and post the Great Vowel Shift:

Spelling   < 1350   > 1600

a..e       /aː/     /eɪ/
e..e       /eː/     /iː/
ea         /ɛː/     /iː/
i..e       /iː/     /aɪ/
o..e       /ɔː/     /oʊ/
oo         /oː/     /uː/
u..e       /uː/     /aʊ/ (like the "ow" in "how", or the "ou" in "loud")

Today:

Letter     "Short"  "Long"
a          /æ/      /eɪ/
e          /ɛ/      /iː/
i          /ɪ/      /aɪ/
o          /ɒ/      /oʊ/
u          /ʌ/      /juː/

As you can see from the table the "long" and "short" forms of the vowel bear almost no relation to each other anymore. I was also taught as a child that each vowel has a single sound value, when there are actually multiple sound values for each letter. I once tried teaching an ESL student about long and short vowels and they immediately became so confused because the long sounds are not predictable from the short ones that I stopped calling them "long" and "short" at once.

I can somewhat understand teaching children this way; getting them used to the sounds each combination of letters frequently makes is more important to their reading skills than getting the terminology spot on. When they're older, it's not worth going back and correcting the terminology. In fact, it could even be confusing.

Since the current description is over 400 years old and doesn't apply to English as it's spoken today (except that diphthongs are usually sounded for longer than monophthongs), what is an accurate way of describing these two groups of vowels that could be taught equally well to young native speakers as well as adult ESL learners?