Really dull bed dilemma

[WhatAmISupposedToBeDoing]

DD(4) is in the toddler bed evolution of a cot bed. DS(18 months) is in a small cot, as he was in my room until very recently. He is now outgrowing the small cot. They will be sharing the room for the foreseeable future.

Do we

1. Rebuild the cot, put DS in it, buy DD a single and worry about DS when he grows out of the cot
2. Buy 2 low singles and transfer DS straight into a bed with bed rails?

He is fed to sleep then put down, and this is probably going to continue for a while yet. He sleeps pretty well.

We did 1 with the same gap, then when Ds2 outgrew the toddler bed, when he was almost 5, got bunk beds.

Just buy one bed for now, they may want bunks by the time DS grows out of the cot bed!

We have a 19 month gap and when mine were 3 and 18 months I bought 2 standard singles and they went straight into them (DD1 was previously in toddler bed and DD2 in a cot). It was absolutely fine, no issues. Both happily still in their singles at 4 and 3.

By 2yo each time my DDs were in standard single beds. No rails but we did put a rolled up towel down the edge under the sheets (thanks MN!)

Rails are a waste of money IMO - Just ensure there is nothing they could fall onto that will hurt; if you are worried keep the mattress from cot/toddler bed on the floor next to the bed until they have learned not to fall out. Rails can mean the toddler climbs over and falls from a greater height.