Blanket Sleepers are great. Mine wore them through the winter when they were 2.5. We potty trained starting that spring and switched to only 2 piece pj's. By that time they could handle their blankets themselves and the ones we used were crocheted by grandma and not too thick. It was more for comfort than warmth.

Also Carters makes 2-piece jammies out of the super soft blanket sleeper fleece if you want 2 piece for older kids.

MonsterMom6
10 year old ^b^ b twins @ 30w5d (1 survivor) and
8 year old gggg quads @ 32w0d