It may be a problem. The way you have it means that the transformer's VA rating is being split, one half goes to the LCDuino-1, LCD display, motor pot, and four δ1/δ2 boards, and the other half for the 5V relay. 7.5VA is a bit borderline during startup of the LCDuino-1 and friends, and the 5V relay gets its own 7.5VA, which is capable of 7.5VA/9V = 0.83A of current, but it only needs about 1/10 of that. So much of that 7.5VA is wasted.
You can get around this either by going to a larger trafo, or wiring all the 5V consumers to the same rail, and connect the two secondaries in parallel for that rail (the second rail would then be unpowered/unused).
P.S. I get the impression that you are using two δ1 and two δ2 boards, right? If you're using only one of each, then 7.5VA should be enough. The recommendation for LCDuino-1 and only one δ1 and one δ2 board is a 5VA trafo, but that does not take into account the additional draw of the 5V relay.