Trikes or Bikes??

So we have decided to get DD a bike for Christmas - I'm thinking a 40cm one so she has a bit of grow room plus she is tall for her age so think this would suit her.

However we have been tossing up wether to get the twins a bike each or a trike each, they are 2 1/2. DD has a trike which one of the twins rides and is really good with the pedals etc, so I'm thinking of getting them bikes and helmets as I feel this would be better for them but DH thinks we should get them trikes.

What would you do?? If I got them bikes I would be getting the small 30cm ones - and they are tall for their age - but I think it would be a better use of money instead of getting trikes and then having to upgrade to bikes next year anyway.

DS was given a 40cm bike for Christmas just before he turned 3. It's still way too big for him now. He's about 105cm tall. He sits on it but he struggles with the pedals because the bike is just too big for him. He mainly rides his balance bike. We are considering getting him a smaller pedal bike. We got DD a balance bike recently and it is a bit big for her even on the lowest seat setting. She just wheels it around. I wouldn't bother with trikes personally. We have one which was good when I used to walk with DS before DD was born but now it's really just a waste of space. He never used the pedals, I just pushed him around.

I'm looking at the bikes which have the push handle attached so probably would be the best option. I think they will get so much more use out of a bike than a trike. :)

Get them balance bikes.

Balance bikes probably wouldn't work but thanks for the suggestions. With the twins ASD one of them is wheel obsessed and I don't think that he would attempt to ride without pedals as he would be more obsessed with trying to spin the wheels by hand lol :)

Have you been to a shop and tried them out on a bike?
The reason I ask is, the Christmas before last we wanted to get a bike for DS. He was 3 in the Feb after Christmas. He loves things with wheels too and spent ages fiddling with DD1's bike, but when we tried him on one for size he had a fit. We'd never noticed before, but he had never sat on one, and just didn't want to. Fast forward to last October and he started asking about a bike so we got him one with training wheels from Santa. Remembering the kid has never even sat on a bike. 3 weeks later we took the training wheels off. He did however have a little 3 wheeled bug bike with scooter wheels that went really fast and he loved that.
DD2 (3yo height 20monther) has a little bike (30cm) and while it's fine for size, she has no concept of pedals or balance and just gets cranky on it. Thankfully that was a gift, as like you I would hated to have spent money on something only to have to upgrade by the time she can actually ride a bike.