Hi
Although all parts of the routine are connected I would probably look at the short naps at day care as a separate issue really. Short naps are more likely to be due to the time she is put down, the wind down routine and environment, or lack of independent sleeping, rather than the need for solids. I really wouldn't expect solids to help her sleep better at day care.
Mine remained on a 3hr E routine up to 6 months as he had silent reflux and smaller feeds more frequently suited him, but his A times and naps still progressed to a suitable routine for his age. I see you've posted on the naps board for support there
The 'ideal' feeding routine really would be what suits your LO and your family. If she is enjoying her solids meals and her milk intake is stable it is fine to introduce a second meal. Probably the most common routine is to feed milk at the regular E times, and not change these, then to offer the solids meal (1, 2 or 3 when ready - no hurry though) about an hour after the milk feed, this gives them time to build up a small appetite to taste the new foods without being too hungry or disturbing the milk intake. It's also fine to introduce finger foods at this age for LO to begin to self feed, you could offer alongside puree food if you want to spoon feed or choose 1 meal per day which is finger food only.
Like any new skill or development food can disturb sleep at first, guts too as they adapt to the new foods. I'd suggest keeping the last meal of the day much earlier so there is time for her to digest and let any gas out before BT. For this reason you might choose to give breakfast and lunch in the early days and wait until she is older before introducing a third meal in the evening. Feeding earlier in the day also gives plenty of time to notice any adverse reactions to the new foods.
I found the last meal needed to be super early, around 4pm/4.30pm (an hour or so after the 3pm milk). If you want her to join you at the table for your family meal at 6.30pm I would probably just give her a piece of finger food off your plate, or a finger of toast, to explore rather than a full meal that way she will enjoy the social aspect of the meal without taking in too much to make her gassy at night time.
There's no harm in keeping some freshly cooked vegetables from the evening meal and offering them to her at breakfast instead.
FWIW my 3.5 yo still has early dinner, we eat between 4.30 - 5.00pm for our evening meal as this suits his needs (6pm start BT routine, 7pm sleep). It does feel too early for the adults but we have a supper later on if we are hungry.
