Bunkbeds for 20 month old and 7yr old

[Chrysanthamum]

Bunkbeds will soon be the best option for our toddler and 7yr old son. My concern is that the toddler might get up in the night and get his hands on sthing unsuitable that our older boy has been playing with. He plays in his big brother's room all the time and does not put anything in his mouth but we always keep an eye on him. If we're asleep we can't do this obviously. We can wait for a few months before we move them in together. Does anyone else have children with a big age gap in bunkbeds? What are the pitfalls?
Also should I get the beds now or wait until the January sales?

There is a 6 year age gap between my Ds's.

When I moved them in the same room together, I gave the eldest the top bed. I used wooden beds.

Then I used the bed to create a temp seperation.

Boarded up lower bunk by the ladder, and on one end, leaving enough space for Ds1 to play. Put safety gate across wall/bed

Kept other side open for Ds2 to get in and out of bed. Ds1 was very happy and sometimes let Ds2 in his 'room' .

We did have to remove the lower step on the ladder to stop Ds2 climbing up it