I think Megan goes well with your sibset. That said, I do agree with a previous poster that Luke and Elliot are more "current" while Megan is a bit dated. I know LOTS of Megans in their 20s and 30s but only one under the age of five. However, that could be a good thing if you are looking for a classic but not common name. I do love the nickname Meggie!
Other names I thought of were:
May/Mae (I prefer the Mae spelling)
Maisie (nickname for Margaret, but can be used in its own right too)
I Also like Madeline and Matilda and the cute nicknames you picked for them!
One more question - Is Libby's full name Elizabeth? If so, I would suggest using Margaret as a full name and Megan/ Meggie as a nickname. Margaret and Elizabeth are beautiful, classic names and flow better than Elizabeth and Megan, at least in my opinion. I also like Madeline and Elizabeth...
I have never been a big fan of Megan. I think Madeline works much better with your kids' names. Here are my favorite M names:
Hmmm...as someone with the name in question, I have always felt like my name was very dated and is not aging well. I am in my mid 20's and have thought about this often.
The pros...there wasn't a lot of teasing potential in the name, it might be refreshing on a baby/child in 2013, and it isn't a BAD name.
Also, with my maiden name, my initials were MMM and I loved it. So I am all for having same initials!!! I like pp suggestions of Matilda. I also think that Mae would be beautiful with Libby, Luke and Elliot. Good luck! :)
I love the alliteration (for some reason, M alliteration sounds amazing to me), but I don't love Megan. It's still dated to me, but it is soft, sweet, and sturdy sounding. Perhaps there's another M name that "feels" like Megan but is a bit more updated.
With Luke, Elliot, & Libby, I'd suggest:
I do like Megan, and I think it works for you. I think the dated feeling probably depends on where you are - I think it's less dated in the UK.
If I remember rightly from one of your other threads, Libby has the full name Elizabeth, yeah? If so, I think a longer name with a shorter nickname would go well for a girl. Madeleine nn Maddy and Matilda nn Tilly both work well, classics with cute, spunky nicknames. If you've a one syllable surname I'd stick to longer names as well.
Melissa nn Mel or Lissy - might be too close to Elliot or Libby with the nicknames though, but if you can find another one you like - Missy maybe? - it would work.
Millicent/Milena/Mildred nn Milly/Millie - If I've got your surname right, Milly M sounds adorable. Or Amelia/Emilia nn Milly, but that won't give you the MM initials.
Marianna/Marianne nn Mari or Anna/Annie- yes it looks like two names rolled into one, but it's got a load of cute nicknames that would fit right in with your kids' names.
I am a Meghan, I go by Meg, and I love my name. :). My favorite names for a little girl that starts with "m" are: